# Download Friction and Gravity

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```Friction and Gravity
Use pages 380-388 in your textbook to answer the following problems.
1. What is the name of the force that exerts itself when one surface rubs against another?
2. What does a smooth surface look like under a microscope?
3. If you push a book across the floor, it will eventually come to rest (stop). Explain
why this happens in relation to Newton’s first law. (Use page 47 to find the answer.)
4. What does the strength of the force of friction depend on?
5. Give three example of how friction is useful.
6. What is sliding friction? What is rolling friction? What is fluid friction?
Which type of friction requires the most force to overcome?
7. What is the name of the force that pulls objects toward the center of the Earth?
8. What is free fall? Are objects in freefall experiencing balanced or unbalanced forces?
Do objects in freefall accelerate?
9. What is the velocity of an object that falls to Earth after 4 seconds?
10. If you throw a ball forward and drop one from the same height which ball hits the
ground first?
11. What is air resistance? How does surface area affect air resistance? Which will hit
the ground first an acorn or a leaf? Explain your answer.
12. What is weight? What is mass?
13. What is the formula for weight? What is the weight of a 100 kg person on the
Earth’s surface?
14. What is the law of universal gravity? The force of gravitational attraction on two
objects varies with what two things? (figure 13, page 52)
15. Why don’t you notice objects being attracted to your body due to gravity?
16. Explain how your mass would remain the same on the Moon but your weight would
change.
17. The Moon’s mass is 1∕6 that of the Earth. What would you weigh on the Moon?
```
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