Friction

Friction was our topic this week. We started out class predicting what would happen if the students pushed a textbook across the table. We then talked about what made the book stop. The students knew that friction acted on the book, causing it to slow down and eventually stop. I took this opportunity to review Newton's First Law of Motion (inertia) with the students.

I moved on to ask if the class had ever seen gymnastics on TV. I asked if they had seen the gymnasts rub a white powder on their hands. Ballet dancers will often rub the same powder on the bottom of their shoes before dancing on a smooth floor. I asked the students why they do this. Gymnasts and dancers use rosin to create friction between their skin or shoes and the floor or gym equipment. This creates more grip for them.

Friction is a force that opposes motion between two surfaces that are touching each other. In other words, friction is what happens when two things rub or roll against each other. This could be your two hands rubbing together, skis rubbing on the snow, or a hammer hitting a nail. When two objects are touching, their surfaces tend to stick together like the tiny loops and hooks of Velcro.

Would you expect more friction between an oily floor and a slick leather shoe sole or between a rough sidewalk and the bottom of a tennis shoe?
The amount of friction depends on two factors: The kinds of surfaces and the force pressing the surfaces together.

Sliding Friction: This is what we observed when we pushed the textbook across the table. Sliding friction is caused by two objects touching each other and sliding past one another.

Rolling Friction: This uses wheels. Only the bottom of each wheel is in contact with the ground/road so rolling friction is less than sliding friction. The students each rolled a toy car across the table and observed how quickly it was able to move.

Fluid Friction: When an object comes in contact with a fluid (in the form of a liquid or gas), it is considered fluid friction. Airplanes and race cars are streamlined to reduce fluid friction. They have smooth, curved surfaces to reduce the friction, known as drag, with the air.

We completed three experiments to demonstrate rolling and sliding friction as well as the effect of weight on friction.

1) Roller lab.

For this experiment, the students each had two books. They tied a piece of string around one of the books and then tied a rubber band onto the end of the string. The students placed a second book on top and then moved the books by pulling on the rubber band and measured how far the rubber band stretches.

Each student was then given ten round markers. They used the markers to make "wheels" for the books and tried the experiment again. New measurements were taken and we compared the results.
The rubber band stretched more when the bottom book was placed flat against the table than when it was placed on the pens. This showed that things that roll cause less friction than things that slide.

2) Farther lab.

This lab showed the effect of weight on the energy of a moving object.
The students were given two books, 1 small round jar, and 1 large round jar. They set the books up with the edge of one book on the second book in order to form an incline. The students then placed the small jar at the top of the incline and let it roll down. We used a tape measure to see how far the small jar rolled then repeated the experiment with the larger jar.
The larger, heavier jar rolled farther than the smaller, lighter jar. The friction of the books, air, and floor remains constant during the two experiments. The major difference in this experiment, then, is the weight of the two jars. As the weight of a rolling object increases, its energy increases. This means the heavier jar has more energy and will roll farther than the smaller jar.

3) Wobbler lab.

This lab also involved a jar and books that we used to form an incline. Before we started, I had the students predict if an empty jar or a jar with water would roll farther. They predicted the heavier jar with water would go farther. The students started out letting the empty jar roll down the incline. They then measured how far the jar rolled. I then filled the jar about three-quarters full with water. After securing the lid, the students then let the jar roll down the incline and measured the distance it rolled.
Contrary to what they learned in their last lab, the heavier jar in this experiment did not roll as far. :)
In this lab, the friction of the jar did not remain constant. The water in the jar sloshed around, increasing the friction inside the jar. It takes more energy to move the jar with the water swishing around inside.

We wrapped up our discussion of friction by talking about the advantages and disadvantages of friction and then completed one last friction-related lab.

How Far?

This lab showed how the texture of a surface affects motion.
The students were each given a piece of poster board, a piece of wax paper, and a piece of sand paper. They also each had a bottle of glue, a rubber band, some string, and a paper clip. I had pre-cut the poster board with a small horizontal slit to hold the paper clip and then attached the rubber band to the paper clip. The students looped the string through the rubber band and placed the poster board on the table. They placed the glue bottle at the end of the poster board and then pulled the string just enough to straighten the rubber band.
They then pulled the poster board along three different surfaces (the table, the sand paper, and the wax paper) and measured how far the rubber band moved each time.
The wax paper had the least amount of friction so the rubber band stretched the least when the poster board was placed on this surface. The sand paper had the greatest amount of friction, causing the rubber band to stretch a lot.

Baby carrot submarines.

This was a lab we didn't get to last week so I'd made myself a note to do this one at the beginning of class today. I got all excited about teaching friction that I completely forgot! Luckily, we had a few minutes at the end of class today to complete this buoyancy experiment.
Parents may remember those little plastic submarines that used to come in cereal boxes (I know my siblings and I had quite a few!) This is a really fun experiment to try at home.
Cut a baby carrot in half then use a flat-head screwdriver to make a hole in the cut side of the carrot. Break two toothpicks in half and insert the pieces in the rounded part of the carrot (2 on each end).
Fill the hole in the carrot with baking powder and then place your sub in a bowl of room-temperature water.

 At first, the carrot submarine is more dense than the water. However, when the baking powder and water react, they produce a gas (carbon dioxide) that is less dense than the water. This causes the carrot to rise to the surface. When the bubbles dissipate, the carrot will sink back to the bottom. This will continue until all the baking powder is gone.

Reminder: There will be no class next Thursday, November 11th, in honor of the Veterans Day holiday.

To look forward to on November 18th: Kinetic and Potential Energy; The Law of Conservation of Energy

The labs "Roller," "Farther," "Wobbler," and "How Far?" are from Physics for Every Kid.
VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

I found the baby carrot submarine directions on this website:
http://www.coolscienceclub.tripod.com/baking_powder_submarine.html

October 28th - Buoyancy

We continued our discussion of buoyancy today. We started out reviewing displacement and then seeing how displacement, density, and buoyancy are related.

Density can be described as a way of comparing the "heaviness" of materials. I gave the students an example of a basketball and a rock that weigh the same. The rock is smaller than the basketball but it is heavier. Since the rock has its weight held in a smaller package, the rock is denser than the basketball. 

The first activity today was a demonstration lab - "Mover." For this lab, we had a plastic water bottle that I cut the top off to make a funnel. The bottom of the bottle was filled with cold tap water that we added four ice cubes to. We then filled a measuring cup with warm tap water and added blue food coloring to the warm water. Using the funnel, I poured the warm blue water into the ice cold water while the students observed what happened. We noticed the blue water rise to the top of the bottle.
This happens because cold water is denser than warm water. This is due to the cold water contracting while the warm water expands. A drop of cold water, then, is more dense than a drop of warm water. The dense cold water settled in the bottom of the bottle while the less dense warm water rises. This also explains why the surface of the ocean feels warmer than deeper water in the same section of ocean.

I then dropped a nail in a glass of water and asked the students why, if the small nail sank, can large cruise ships and aircraft carriers float? The students provided some suggestions and we completed the lab, "Floating Boat," to find out.

For the "Floating Boat" lab, the students were each given two 12-inch squares of aluminum foil and 20 paper clips. The students placed 10 paper clips on one of the pieces of foil and scrunched the foil into a tight ball. They then created a square boat with the other piece of foil and placed the remaining 10 paper clips into the foil boat.

The students each placed their boats and foil balls into a bucket of water. The boats floated as they were supposed to. The balls were supposed to sink but ours all floated!

Even though the ball and boat have the same weight, the ball takes up a smaller space making it the denser object. The ball pushes less water out of the way than the boat so there is not (should not be) enough upward force to cause the ball to float.
Large ships are able to float, despite their great weight, because they have hollow compartments that are filled with air. This air increases their buoyancy.

Continuing our discussion of buoyancy and buoyant force, we moved on to discuss differences in salt water and fresh water. I asked the students if there is a difference in the buoyant force of fresh water and salt water. I also asked which one they thought had a greater buoyant force. To test their hypotheses, the students completed a hydrometer lab. For this, we filled a pen cap with modeling clay and then dropped it in a jar of tap (fresh) water. The students then added salt (1 tablespoon at a time) and observed the changes in the pen cap. We found that adding salt caused the pen cap to gradually float to the top of the jar.

The hydrometer lab led into a discussion of the Dead Sea. The Dead Sea is the lowest point on earth. Its elevation is 1,300 feet below sea level! We compared this to the elevation of Vista which is 563 feet above sea level. The Dead Sea is also the saltiest body of water on earth - it is almost 10 times saltier than any of earth's oceans! The minerals in the Dead Sea make the water so dense that people are able to bob on the surface like a piece of cork.

We finished the class session with two last lab projects: "Risers" and "Subs."

For "Risers" the students were each given a clear plastic cup, club soda, and some modeling clay. They divided the modeling clay into five rice-sized pieces and added club soda to the cups. The students immediately dropped the pieces of clay into the cups of soda and watched what happened. The carbon dioxide bubbles in the soda stuck to the clay causing the balls of clay to be light enough to rise to the surface of the cup. Once the clay reaches the top, the bubbles are knocked off and the clay sinks back to the bottom of the cup.

To complete the "Subs" lab, each student was given a plastic cup and a flexible drinking straw. Each student had a turn placing the cup on its side and pushing it beneath the surface of a bowl full of water. They then turned the cup so it sat upside down on the bottom of the bowl. Each student slipped the end of the straw under the rim of the glass and blew through the straw while supporting the glass with one hand (while trying not to restrict the movement of the glass). The students observed that the glass tried to rise to the surface of the water while they were blowing into the straw.

 

In order for submarines to sink, special tanks on the subs are filled with water. This is similar to the students filling their cups with water. To allow the sub to surface, the water in the tanks is replaced with air. We demonstrated that by blowing into the cups. The air makes the submarines more buoyant, allowing them to float to the surface.

To look forward to next week: Friction!

The labs Floating Boat and Risers are from Physics for Every Kid.
VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

The labs Mover, Hydrometer, and Subs are from 200 Gooey, Slippery, Slimy, Weird, and Fun Experiments.
VanCleave, J. (1993). 200 Gooey, Slippery, Slimy, Weird, and Fun Experiments. New York: John Wiley and Sons, Inc.

October 21 - Center of Gravity, Buoyancy

The students learned about center of gravity this week. We also began an introduction to buoyancy.

I gave the students three kinesthetic tasks to begin the lesson. See if you can do these at home!

1) The Impossible Leap

Bend over and hold your toes with your hands while keeping your knees slightly bent. Now try to jump forward while remaining in that position. Don't unbend your knees or take your hands away from your toes. Can you jump?

2) The Super Glue Chair
Sit in a straight-backed, armless chair with your feet planted flat on the floor and your arms folded across your chest. Now try to stand up while keeping your feet flat and your back straight. Can you do it?

3) Pick Up Trick

Place a pencil (or other object) on the floor about 20 inches from the wall. Stand with your back and heels flat against the wall. Keep your feet together. Try to pick up the object without moving your feet or bending your knees. Can you do it?

These experiments all demonstrate center of gravity. Center of gravity can be described as the point at which the entire weight of a person or object is concentrated or held. In symmetrical objects, the center of gravity is the geometric center of that object. In non-symmetrical objects, such as the human body, the center of gravity changes with every movement we make. In the experiments above, the students' centers of gravity changed each time. Here are explanations of what happened in each task:
The impossible leap. If you were to re-do this but jumped backward you would have no problem. When a person jumps, their center of gravity shifts in the direction they want to jump. To prevent falling over, the person must move their base of support in that same direction. The students were unable to jump forward because they would need to use their toes (base of support) to do so.
The super glue chair. When a person sits down, their center of gravity is at the base of their spine. If you try to stand up while keeping your back straight, your center of gravity is unable to move to a position above your feet (where you need support to stand).
Pick up trick. When standing straight against the wall a person's center of gravity is over their feet. Normally, when a person bends over, their center of gravity moves forward. In order to maintain their balance in this trick, the students would have had to move their feet. Since they weren't able to do this, they weren't able to pick up the pencils.

After discussing the center of gravity movement activities, the students completed a lab ("Shake Up") to show how shape affects speed. They had three objects - a roll of masking tape, a marble, and two jar lids that were taped together. The students predicted which they thought would roll to the end of a tilted table first. The students then let the objects go and observed what happened.

The marble reached the end of the ramp first. This is due to the marble's small size. Because of this, the marble's center of gravity is closest to its overall weight. The slowest object was the roll of tape since it was the largest and its center of gravity is furthest from its overall weight. We decided that this would be more obvious if we had a larger roll of tape. :)

We moved on to begin a lesson on buoyancy that we will continue next week. I placed 1 cup of water into a glass measuring jug and asked the students what they thought would happen to the water level if I added an ice cube. They correctly guessed that the water level would rise. I then asked them how many ice cubes I would need to add to raise the water level by 1/4 cup, 1/2 cup, and 1 cup. The students made predictions for each and we tried each one out.
The raising of the water level when something is added to the water is called displacement. The ice cube displaced or pushed away some of the water causing the level in the jug to rise. We then spoke a little about Archimedes and Archimedes' Principle (displacement and the idea that the weight of the water displaced by an object is equal to the buoyant force in the water).
We also talked a little about buoyant force. Buoyancy is a pushing force while gravity is a pulling force. When we put the ice cube in the jug of water, we noticed that only part of the ice cube stayed above water. This is because gravity is trying to pull the ice cube down to the bottom of the jug while buoyancy is pushing it up to the top of the water/jug. 

The experiments "The Impossible Leap," "The Super Glue Chair," and "Pick Up Trick" are all from this website: http://www.escapadedirect.com/plwigr.html
The "Shake Up" lab is from Physics for Every Kid.
VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

October 14 - Gravity

We began class by discussing what the students already know about gravity. I also asked them how gravity affects human beings.

Each student was then given a sheet of notebook paper and a hardcover textbook. The students were asked to predict what would happen if they dropped the book and paper separately. Would the book or paper fall fastest? We tried this and then predicted what would happen if the paper was placed on top of the book. Again, the students tried the experiment and discussed their observations.

Gravity pulled equally on the book and the paper. So, even though the book hit the ground before the paper when we dropped them separately, gravity's pull on each object was equal. The paper fell at a slower speed due to air resistance. The book's weight overcame the force of the air but the paper, being so much lighter, had little effect on the air's push. This made it fall at a much slower rate.

Gravity is a force that attracts all objects to each other. This attraction is called Gravitational Pull. On Earth, gravity keeps an atmosphere around the planet. It also causes things to fall to the ground, causes the ocean's tides, and causes hot air to rise while cool air falls (which leads to winds).

Gravity pulls things to the center of the Earth. Gravity also gives people and objects weight. Since the force of gravity is different on other planets, people and objects can weigh more or less than they do on Earth on other planets.
Here is a link to a fun website you can use to discover weights of people, pets, or objects on other planets: http://www.exploratorium.edu/ronh/weight/

We completed several other experiments about gravity this week. Here are the details.
*Bigger - In this lab, students made two parachutes each to determine if size affects the speed of a falling parachute.
Each student was given a 12-inch square of plastic (cut from a plastic bag), a 24-inch square of plastic, 8 20-inch pieces of string, 2 washers, and 2 4-inch pieces of string. They used these materials to construct parachutes and then predicted which they thought would hit the ground first (similar to the book and paper experiment from the beginning of the class session). We found that the parachute made from the larger bag fell to the ground more slowly than the smaller parachute. Just like in the book and paper experiment, this is due to air resistance. The larger parachute has a larger surface area and a small weight so it has more air resistance. 

*Gravity Won - The students learned about water's surface tension in a previous lesson. This lab demonstrated the effect of gravity on weak surface tension.
We filled a baby food jar with rubbing alcohol then colored it with food coloring. A straw was placed into the jar of alcohol and held in place with a small piece of modeling clay. When we tipped the jar upside down, the alcohol flowed out of the jar and the straw.
Alcohol has a weaker surface tension than water meaning the attraction between the alcohol molecules is not very strong. The air pressure inside the straw was not enough to hold liquid in the straw so the pull of gravity caused the liquid to flow out of the straw.

*Anti-Gravity - This was very similar to the last lab except we used water instead of rubbing alcohol. Since water has a greater surface tension than alcohol, the air pressure inside the straw pushed up on the water when the jar was tipped upside down while the water molecules pulled from side to side. These pushing and pulling forces were greater than the pull of gravity so the water remained in the straw.

The labs "Same Speed" (book and paper) and "Bigger" are from Physics for Every Kid.

VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

The labs "Gravity Won" and "Anti-Gravity" are from Chemistry for Every Kid.
VanCleave, J. (1989). Chemistry for Every Kid: 101 Easy Experiments That Really Work. San Francisco: Jossey-Bass. 

October 7 - Motion: Inertia; Newton's Laws of Motion

We continued our study of motion this week by covering inertia (Newton's First Law of Motion) as well as Newton's Second and Third Laws of Motion.

Inertia is the tendency of an object to resist any change in its motion. If an object is at rest, it will remain at rest until it is acted upon by a force. If the object is moving, it will continue to move until acted upon.

We started our session with a lab. This lab was "Crash!" from Janice VanCleave's Physics for Every Kid. Each student had a small piece of modeling clay, 2 rulers, a toy car, a pencil, and 2 books. For the first part of the lab, the students set up a ramp using one book and a ruler. They taped the pencil to their desk about 2 car lengths from the ruler. The students then placed the modeling clay onto the hood of their toy cars and allowed the car to roll down the ruler. The students observed the modeling clay fly off the hood and used the second ruler to measure how far from the car the clay fell. We kept track of the measurements.
After three rolls, the students added a second book to the stack. They made predictions about whether or not the clay would now fly further from the car. Again, they had three rolls and we tracked the measurements.

Once we completed both sets of rolls we discussed how all this related to inertia: when the clay flew off the front of the car, it continued to move even though the car had stopped. As the car rolled down the ruler, its speed increased. The clay was moving at the same speed as the car so, even though the pencil stopped the car, the clay continued to move until gravity acted upon it causing it to fall to the table.

After completing the work with two books, we decided to try it with four.

We moved on to talk about mass and how it relates to inertia. I asked the students if they thought objects with different weights have the same inertia. I used the example of a ping-pong ball, a tennis ball, a basketball, and a bowling ball. The greater an object's mass, the greater its inertia. I also asked them if they would be able to change the velocity of a bowling ball by swatting at it with a ping-pong paddle. We discussed the fact that a greater force would be needed to change the velocity of the bowling ball than would be needed to change that of the ping-pong ball.

The students then completed the lab "More." This lab demonstrated the effect of weight on inertia. The students were given a pair of plastic soda bottles. One bottle was empty; the other was about half full of water. We tied a 12-inch piece of string to a rubber band and then slipped the rubber band onto the bottom of the empty soda bottle. Before we began, I had the students predict which one would have a greater inertia or a greater resistance to motion. The students each pulled on the string to drag the empty bottle across the table. We measured how far the rubber band pulled away from the bottle and recorded our results. We then did the same with the half full bottle. The students discussed that since the bottle with water was heavier than the empty bottle, it had a greater inertia that caused the rubber band to pull away further from this bottle.

We then discussed Newton's Second and Third Laws. I used the example of hitting a baseball versus a bowling ball to describe Newton's Second Law: The Law of Force (Force = Mass x Acceleration). They understood that since the bowling ball has a greater mass, it would require a greater force to hit the bowling ball with a baseball bat.

Newton's Third Law is the law of action and reaction. Whenever an object pushes on another object, the first object gets pushed back in the opposite direction equally hard. We used two labs to demonstrate this concept.
"Balloon Rockets" - Students were given a long piece of string that the threaded a piece of drinking straw onto. They then tied the string to two chairs. Each student then inflated a balloon and taped the balloon onto the straw. The students observed what happened when the balloon was released.
When the balloon was released, it pushed the air out. However, that air pushed back on the balloon (action-reaction), causing the balloon to move forward.

"Paddle Boat" - The students used cardboard to create a simple boat shape. They cut a paddle out of the cardboard and used a rubber band to attach it to the boat. The students then wound up the paddle and placed the boat in a container of water.
When the students wound up the paddle, it turned and hit against the water. The paddle, then, pushed against the water and the water pushed back. This action and reaction caused the boat to move.

We closed up class with one more lab that demonstrated inertia. For this one, I placed five textbooks on the edge of a rolling chair. I pushed the chair across the classroom and then stopped abruptly. Due to inertia, the books remained in motion when the chair stopped. 

To look forward to next week:

We will learn more about Sir Isaac Newton by studying gravity.
We'll find out what some common objects would weight on different planets and we'll complete several experiments about the force of gravity.

The labs "Crash!", "More," "Balloon Rockets," "Plop!" and "Paddle Boat" are from Physics for Every Kid.

VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

September 30 - Motion (Pushes and Pulls), Velocity

We're going to start out the semester learning about forces. Our class on September 30th focused on motion.

We discussed how a force can be a push or a pull and then spent a little time talking about examples of pushes and pulls in our daily lives (pushing or pulling a door open or closed, bending over to pick something up, stretching a rubber band, squeezing a tube of toothpaste, etc).

The students completed three hands-on experiments to observe how things can pull on each other. Our first project, "Floating Sticks," involved the students placing two toothpicks side-by-side in a bowl of water. The students dipped a third toothpick into dish washing detergent and then carefully dipped this third stick into the water between the two floating toothpicks. This lab showed how dish washing detergent breaks up the attraction of water molecules. This causes some water molecules to pull on others, taking the toothpicks with them.

Our second project for the day was "Tug of War." For this one, each student was given a sheet of aluminum foil, 1/2 cup of water that was mixed with blue food coloring, and 1/4 cup of rubbing alcohol. The students placed the foil on the table and then poured a thin layer of the blue water onto the foil. They then used an eyedropper to add a drop of rubbing alcohol to the center of the layer of water.
The water molecules on the surface of the water normally pull equally in all directions. However, when we added the rubbing alcohol, the two liquids immediately separate. The alcohol pulls away from the water while the water pulls away from the alcohol.

We also tried a lab called "Powder Dunk." This one didn't have the desired effect so we may re-try this one at some point during the semester. Each student had two soup bowls filled with water. We sprinkled a thin layer of talcum powder over the surface of the water in each bowl. The students dipped one of their toothpicks in shampoo and the other in the dish soap. They then touched the soapy end of each toothpick to the center of the powder in each bowl. We should have seen the shampoo cause the talcum powder to break up into large floating blocks and the dish soap to cause it to rush to the sides of the bowl and then sink.

Since the talcum powder is water resistant, the pieces of talc will float on top of the water. As we know from the last experiment, water molecules normally pull equally in all directions. Soap or shampoo break up the attraction of the molecules causing the water to move outward. The powder should have followed! Since the liquid dish soap will dissolve in water, it should have caused the little pieces of talcum powder to sink since the water will quickly cover the talc.

We moved on to discuss velocity. Velocity describes the speed and direction of an object. We were going to go outside to move around at different speeds and in different directions to demonstrate changes in velocity but the thunder and rain kept us in the classroom. Instead, I used the example of cars traveling on a road to explain this concept. If two objects (cars) are moving at the same speed and in the same direction, we can say they have the same velocity. However, if one car slows down or speeds up, the velocity of that car has changed. We also discussed cars traveling at the same speed in opposite directions (even though the speed is the same, their velocity is different).

After discussing velocity, we spent a little time talking about balanced and unbalanced forces. Forces on an object that are equal in size but opposite in direction are balanced forces. To explain this, I used the example of playing tug-of-war with a dog. When you plant yourself on the ground, the ground actually pushes back up on you. If you do not move backward or forward, the force of the dog pulling must be equal to the force of the ground pushing on you. The forces of the dog and the ground, then, are equal or balanced.

Now, imagine you are playing tug-of-war with the dog but your foot hits a slippery spot on the ground. The ground is now unable to exert as much force back on you but the dog is still able to pull just as much. Since the pull of the dog is now greater than the push of the ground, the forces acting against you are unbalanced. We also tied in velocity. When the forces are balanced and you are not changing either speed or direction, your velocity remains constant. When you hit the slippery patch of ground and the dog is able to pull you over, you accelerate in the direction of the greater force (in this case, the dog). Therefore, your velocity has changed.

There was one more quick lab to close out the class session. This one, "Fly Away," involved the movement of air due to unequal pressure. Each student was given a small glass soda bottle which they laid on its side on the table. They then squeezed a small piece of notebook paper into a small ball. The students placed the wad of paper just inside the opening of the bottle and then crouched down in front of the bottle to try to blow the paper into the bottle. We had mixed results (probably due to the pieces of paper being too big) but we should have observed the paper ball flying out of the bottle. This happens due to changes in air pressure. Before the students blew into the bottles, the amount of air inside and outside of the bottle are the same. When they blew into the bottles, the amount of air inside the bottle increased, thus increasing the air pressure. That extra air has to go somewhere so it exits through the neck of the bottle, pushing the paper ball out with it.

To look forward to next week:

Inertia and Newton's Laws of Motion
We will be making paddle boats and balloon rockets!

The labs "Floating Sticks," "Tug of War," and "Powder Dunk" are all from Janice VanCleave's Chemistry for Every Kid.
VanCleave, J. (1989). Chemistry for Every Kid: 101 Easy Experiments That Really Work. San Francisco: Jossey-Bass.

The lab "Fly Away" is from Physics for Every Kid.
VanCleave, J. (1991). Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound. San Francisco: Jossey-Bass.

Here's a list of topics we'll cover this semester.

Week 1 (September 23) - Introduction to physical science; the scientific method

Week 2 (September 30) - Motion - balanced and unbalanced forces; velocity

Week 3 (October 7) - Motion - Inertia; Newton's Laws of Motion

Week 4 (October 14) - Gravity

Week 5 (October 21) - Gravity - Archimedes' Principle; center of gravity

Week 6 (October 28) - Buoyancy

Week 7 (November 4) - Friction

*No class November 11 - Veterans' Day Holiday*

Week 8 (November 18) - Kinetic and potential energy; Law of Conservation of Energy

*No class November 25 - Thanksgiving Holiday*

Week 9 (December 2) - Temperature and heat

Week 10 (December 9) - Temperature and heat

Week 11 (December 16) - Simple machines

*No class December 23 or 30 - Winter Break*

Week 12 (January 6) - Simple and compound machines