ANSWER KEY Station #1: Clothespin Lab

Transcription

1 ANSWER KEY Station #1: Clothespin Lab 1. Using the string, tie the ends of the clothespin so that the clothespin is open. 2. Place the cookie sheet, upside-down, on the floor. 3. Place the tied clothespin on top of the overturned cookie sheet so that both halves of the clothespin touch the cookie sheet (not just one half is touching). 4. Place each pencil (one small, one big) on opposite sides of the clothespin, near where it is tied. The pencils should be perpendicular to the clothespin. 5. Use a match to light and burn the string. Try not to burn the clothespin or your fingers. 6. Measure the distance that each pencil travels and record your observations. 7. If there is time, repeat the demonstration using other objects of differing masses. Be sure to record your observations. 1. Explain what you observed using terms that we have learned in this unit. Newton s 2nd Law Force = Mass x Acceleration. The larger pencil did not travel as far as the smaller pencil because it has a greater mass. The force exerted from the clothespin was equal in both directions. Because the force was equal but the masses of pencils were unequal the distance the pencils traveled was not equal. Newton s 1 st Law The pencils stayed at rest until an outside force (flame burning string) was placed upon the pencils and the clothespin open and moved the pencils. The pencils also continued to move but gravity slowed the motion and was the unbalanced force. The force 2. Was the force on each pencil the same? Explain. exerted upon the two pencils was equal because of Newton s 3 rd Law. There is an equal and opposite reaction. The clothespin open with the same force in both directions and so each pencil was hit with the same amount of force. However, upon impact the larger pencil had more force because the acceleration was the same, the force was the same, but the mass was greater with the larger pencil so it hit with more force. This factor is because of Newton s 2 nd Law.

2 3. Give some practical examples of this activity. Firecrackers, nerf guns, stopper on a string gun, dynamite other ideas? Station #2: Dominoes 1. Set up a book to use as a barrier so the dominoes do not leave the table. 2. Stack the dominoes with the widest parts touching each other. Place the stack 8 to 12 inches from the barrier. 3. Use the ruler to hit the bottom domino, sharply, toward the barrier. The bottom domino should be the only one that is dislodged, although other may move a bit. 4. Do the same thing, except this time, hit the domino lightly. 5. Restack the dominoes and attempt to reduce the pile, one domino at a time. 6. Let everyone in the group make this attempt. 4. What happened when you hit the dominoes sharply? The bottom domino (the one hit) sailed in the direction you hit it in. 5. What happened when you hit the pile gently? The entire pile fell over. 6. Were you able to reduce the pile completely? Why do you think this was possible? Yes, by hitting the bottom domino one at a time you could reduce the pile one at a time. This is possible because of Newton s 1 st and 3 rd Law. Newton s 1 st Law states than an object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an unbalanced force. All dominoes except for the bottom one stayed at rest because of Newton s 1 st Law. Newton s 3 rd Law came into play because there was an equal and opposite reaction. The ruler traveled at a speed and hit the bottom domino. The force from the ruler transferred into the bottom domino and now that domino had the equal and opposite force. Plus, the ruler somewhat jerks back (equal and opposite reaction).

3 Station #3: Coin & Egg Lab 1. Place the paper so that part of the paper is on the table and part is hanging off the edge 2. Place one of the coins on the paper that is on the table. 3. Attempt to remove the paper from under the coin with the least disturbance to the coin so that the coin doesn t move much, if at all. Now, 4. Spin each egg on the table, separately. Do not spin the eggs so hard that they fly off the table or into something so that they break! 5. Note what happens as you spin each egg. 6. Which egg do you thing is the hard boiled egg? 7. Explain your reasoning to your group. Try to convince everyone in your group that yours is the correct answer. 8. Let each person in your group do this activity. 7. Were you able to move the coin without disrupting it? Yes, the coins stay in place but the paper moves out from under them. 8. Why is this trick possible? Newton s 1 st Law. The coins wanted to stay in place because they were at rest. There was not an outside force that influenced them. The force that occurred was to the paper. 9. What happened when you spun each egg? The eggs spun at different speeds and consistencies. The eggs that were hardboiled stayed at a level spin. The eggs that were raw changed the level they were spinning at. 10. How does inertia help you decide which is the hard boiled egg? Inertia is a tendency to resist a change in its motion. However, when a raw egg is spun there contents inside the egg will move because of gravity, therefore, jostling the direction and motion of spinning the egg. The hardboiled egg can continue to spin in a steady direction. The following symbols on the eggs indicated if they were raw or hardboiled. They were

4 Station #4: Dropping Objects 1. The student places the three marbles in the groove on the ruler and holds the ruler over his or her own head. 2. Turn the ruler so that all three objects (sphere shaped) drop at the same time, toward the floor, not the table top. (One student should be appointed the retriever, to watch where the marbles go; others in the group should watch the demonstration). 3. Repeat the demonstration so that everyone in the group can be an observer. 4. Do the same thing with a flat piece of paper and a piece of paper that has been balled up. 5. The demonstration may be repeated with the other objects in the lab. 11. Could you tell which object hit the floor first? If so, explain why you think that object hit the floor first. Depending on the object you could tell which one hit first. Objects have the same rate of acceleration, but when the masses are different objects that are heavier hit with more force.

5 12. Were forces caused by air important in the investigation? Why? Objects that are aerodynamic will travel through air more quickly than objects that are blunter and do not have as much capability of traveling and cutting through the air. Fluid friction is involved, along with gravity when these objects dropped to the floor. Gravity forces objects to fall. Objects slow down in their fall because of fluid friction. 13. What did you observe when you used different objects? Objects with a greater mass fell with more force than objects that were lighter (ie. The softball fell with more force than the ping pong ball). Station #5: Car Crash 1. Set up a ramp that is two textbooks high with a barrier at the bottom of the ramp that will stop the rolling vehicle. 2. Place the Ping-Pong ball in the vehicle in such a way that it will fly out of the vehicle upon impact with the barrier. 3. Place the vehicle with its passenger (ping pong ball) at the top of the ramp and let it roll down the ramp. Do not shove or push the car down the ramp!) 4. Increase the height of the ramp and repeat the demonstration, recording observations. 5. Use a thread or string to tie the passenger into the vehicle, and repeat the demonstration. 14. What happened to the passenger in the first trial? Why? The ping pong ball passenger flew out of the car. This occurred because of Newton s 1 st Law. An object in motion will continue in motion. The car stopped but the ping pong ball continued to travel because it wasn t truly attached to the car. 15. How far did the passenger travel from the vehicle in the first trial? Further than the car without wearing a seatbelt and the same distance as the car when wearing a seatbelt. 16. Did the height of the ramp make a difference in how far the passenger traveled? How? Why? The car traveled faster with a steeper ramp and the ping pong ball went further with increased acceleration. There was a stronger

6 force with greater acceleration. 17. Could you make a better seat belt? Explain it. Current seatbelts in cars are designed well because they strap both the lap and upper body of the passenger. There would probably be a better design to strap the ping pong ball into the car depending upon how the student designed it. Station #6: Vinegar & Baking Soda 1. Put on safety goggles 2. Find the box marked with masking tape on the floor for this activity. 3. Place three straws, side-by-side, on the floor, inside the box. 4. Pour 100mL of vinegar into the bottle. Then lay the bottle on its side, making sure the vinegar does not leak out. Then place the bottle horizontally on top of the straws. (The length of the bottle should lay across all three of the straws). The bottle top should be facing away from the classroom and students. 5. Coat the rubber stopper or cork with petroleum jelly. 6. Place two tablespoons of soda on a piece of tissue, roll the tissue and twist the ends. 7. Put the wrapped tissue in the bottle and quickly fit the stopper or cork loosely but securely into the mouth of the bottle. Do NOT force the stopper/cork in tightly!!! Be sure the tissue paper and its contents are in contact with the vinegar. 8. BE SURE THAT EVERYONE, including students that are not in your group, STANDS TO THE SIDES OF THE BOTTLE... not in front or behind the bottle. 9. Observe what happens and record measurements. **Once the stopper/cork is in the bottle, students should not touch the bottle until the stopper/cork is expelled. Should any adjustments need to be made or the demonstration does not seem to work, the teacher must assist. 10. CLEAN-up-- washout the bottle; throw tissue away; use soap to clean stopper/cork; return materials and supplies; wash/dry goggles; wipe table and floor, if needed. 18. What happened when the vinegar and soda mixed? The vinegar and soda reacted and bubbled. 19. Did the stopper fly out of the bottle? If so, in which direction did it go? Yes, the stopper flew out in the direction that it was pushed.

7 The reaction occurred and forced the stopper out. Because the stopper was being pushed out of the bottle it continued to travel in the direction that the gas (Carbon Dioxide) was trying to escape. 20. Did the bottle move? If so, which direction? Yes, in the opposite direction of where the stopper traveled. 21. How could Newton s 3rd Law be used to explain what happened? For every action there is an equal and opposite reaction. The bottle and stopped traveled in opposite directions because of Newton s 3 rd Law. Both objects moved in opposite directions because of the force that occurred. 22. How could Newton s 2nd Law be used to explain what happened? Newton s 2 nd Law states that Force = Mass x Acceleration.. The bottle traveled in one direction but not as far because it has greater mass than the stopper. The stopper traveled further because it has less mass. Station #7: Inertia is Nuts 1. Balance an embroidery hoop vertically on the flask's mouth. 2. Stack nuts on the top of the hoop. Using one hand, snatch the hoop away quickly so that the nuts will fall into the flask. 3. Perform the activity and create a contest to see who can get the most nuts at once into the flask. 23. Explain what inertia has to do with this station. Inertia is the resistance to change in motion. The nuts stayed stacked on top of each other because they wanted to remain in rest. However, gravity interfered and pulled them down into the Erlenmeyer Flask. 24. Describe the challenges you had with this lab station. The greater the amount of nut used, the harder it was to balance them. With too slow of motion to grab the masking tape roll, the nuts had more chance to go in different directions and be influenced by other forces. 25. When else do you see similar actions that you saw in this lab? Can you think of any magic tricks or other situations? Magicians table cloth; Object sitting on ledge of boat and boat takes off, object falls in water, etc. Students will have various answers.

8 26. How does this station relate to science? Newton s 1 st Law Objects in rest want to stay in rest. Newton s 2 nd Law With faster acceleration of hand, stronger force put on masking tape roll. Station #8: Balloon Reactions 1. Blow up a balloon using the balloon pumps. 2. Hold the opening downward and release the balloon. 3. Repeat this several times, and observe what happens. 4. Try blowing the balloon up with different amounts of air and observe what happens. 5. Aim the balloon in different directions (away from people) and observe what happens. 27. Explain what happens at this stations using Newton s 3 rd Law. There is an equal and opposite reaction with the air escapes from the balloon. The air escapes one direction and pushes the balloon in the other direction. Newton s 3 rd Law states that there is an equal and opposite reaction. 28. How did the amount the balloon travel vary when changing the amounts of air in the balloon? The more air placed in the balloon, the further the balloon traveled. 29. Does the distance the balloon travels vary with how you aim the balloon? For example, when you aim the balloon upwards versus downwards, does the distance it travels change? When holding the balloon upwards it is going against gravity and does not travel as fall. The balloon is interacting with fluid friction and gravity throughout the course of its path. 30. List two other examples of when you see Newton s Third Law occurring. Bird flying; baseball and bat; 2 figure skaters pushing away from each other, etc.