Test 2 Review

These problems are good examples of problems that will appear on the test. All returned homework is also fair game. This review is not for a grade.

1. What is a force? What are the standard units of force? Give an example of a force.
2. What is mass? What are the standard units of mass?
3. What is weight? Find the weight of a 25 kg boulder on Earth.
4. Forces of 10N and 15N act on an object in the same direction. What is the net force?
5. Forces of 10N and 15N act on an object in opposite directions. What is the net force?
6. If an elephant is chasing you, its enormous mass seems very threatening. But if you zigzagged, the elephant’s mass would be to your advantage. Why?
7. Does the law of inertia apply to objects at rest, moving objects, or both? Support your answers with examples.
8. The law of inertia states that no force is needed to maintain motion. Why, then, do you have to keep pedaling your bicycle to keep it going?
9. State Newton’s 1^st Law.
10. State Newton’s 2^nd Law in words and in the form of an equation.
11. Suppose a shopping cart is being accelerated by a certain net force. If a load is dumped into the cart so its mass is doubled, by how much does the acceleration change?
12. Distinguish between force and pressure.
13. Which produces more pressure on the ground: a person standing up or the same person lying down? Explain.
14. If an object has no acceleration (a=0), can you say that no forces are acting on it? Explain and draw a free body diagram as an example.
15. Why does a sharp knife cut better than a dull knife?
16. A crate is pushed across the floor to the left. Which way does the friction force act on the crate?
17. A 60 kg student slides to the left across the linoleum floor in his socks.
1. What is the weight of the student?
2. What is the normal force on the student? What causes this normal force?
3. If the coefficient of kinetic friction is 0.2, what is the force of friction on the student?
4. Draw a free body diagram of the student and find the net force on the student.
5. Find the acceleration of the student.
18. If a bicycle and a truck have a head-on collision, upon which vehicle is the impact force greater? Which vehicle has the greatest change in its motion? Defend your answers.
19. We know that the Earth pulls on the Moon. Does the Moon also pull on the Earth? If so, which pull is stronger?
20. Draw a picture of two teams playing tug-of-war. Include all forces involved. What determines who wins?
21. When you push off the ground (jump up), the Earth really does recoil downward. Why isn’t this motion of the world noticed?
22. If you walk on a log that is floating in the water the log moves backward. Why?