1. Is acceleration proportional to net force, or does acceleration equal net force? |
-acceleration and net force are proportional to each other |
2. When you push horizontally on a crate on a level floor that doesn't slide, how great is the force of friction on the crate? |
-it takes more force to get it going to keep it sliding -the force of friction is opposite and equal to your push |
3. As you increase your push, will friction on the crate increase also? |
-yes. As you increase your push, friction also increases just as much (Ex: if you push with 70 N, the friction builds up to become 70 N) |
4. Once the crate is sliding, how hard do you push to keep it moving at constant velocity? |
-push with force equal to and opposite the friction force |
5. Which is normally greater: static friction or sliding friction on the same object? |
-static friction is greater |
6. How does the force of friction for a sliding object vary with speed? |
-the friction force remains approximately the same whether it is high speed or low speed -not dependent on speed |
7. Does fluid friction vary with speed? |
-yes |
8. Which is more fundamental: mass or weight? |
-mass is more fundamental than weight -weight varies with location, mass does not vary |
9. Fill in the blanks: |
-mass -weight |
10. Fill in the blanks: |
-kilogram (kg) -pounds (lb) |
11. What is the approximate weight of a quarter-pound hamburger after it is cooked? |
-about 1 newton |
12. What is the weight of a 1-kilogram brick resting on a table? |
-about 10 N |
13. In the string-pull illustration in Figure 4.8, a gradual pull of the lower string results in the top string breaking. Does this occur because of the ball's weight or its mass? |
-the string breaks because of the weight of the ball |
14. In the string pull illustration in Figure 4.8, a sharp jerk on the bottom string results in the bottom string breaking. Does this occur because of the ball's weight or its mass? |
-it occurs because of the mass of the ball |
15. Is acceleration directly proportional to mass, or is it inversely proportional to mass? Give an example. |
-acceleration is inversely proportional to mass |
16. State Newton's second law of motion |
-"the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force and is inversely proportional to the mass of the object" |
17. If we say that one quantity is directly proportional to another quantity, does this mean they are equal to each other? Explain briefly, using mass and weight as an example. |
-no. Weight is proportional to mass, but not equal to mass |
18. If the mass of a sliding block is somehow tripled, what happens to the acceleration? |
-the acceleration would also be tripled |
19. If the mass of a sliding block is tripled while a constant net force is applied, by how much does the acceleration change? |
-the acceleration decreases to one-third |
20. If the mass of a sliding block is somehow tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration? |
-the acceleration remains the same |
21. How does the direction of acceleration compare with the direction of the net force that produces it? |
-acceleration and net force are in the same direction |
22. What is the condition for an object experiencing free fall? |
-gravity is the only force acting on the object (friction is negligible) |
23. The ratio circumference/diameter for all circles is Pi. What is the ratio force/mass for freely falling bodies? |
-the ratio of mass is g |
24. Why doesn't a heavy object accelerate more than a light object when both are freely falling? |
-acceleration of free fall is independent of an object's mass -in free fall they have the same acceleration |
25. What is the net force that acts on a 10-N freely falling object? |
-the net force is 10-N |
26. What is the net force that acts on a 10-N falling object when it encounters 4-N of air resistance? 10-N of air resistance? |
-6 N -10 N |
27.What two principal factors affect the force of air resistance on a falling object? |
-speed and frontal area affect the force of the air resistance |
28. What is the acceleration of a falling object that has reached its terminal velocity? |
-acceleration is zero |
29. Why does a heavy parachutist fall faster than a lighter parachutist who wears a parachute of the same size? |
-a heavier parachutist must fall faster for air resistance to balance weight |
30. If two objects of the same size fall through the air at different speeds, which encounters the greater air resistance? |
-the faster object encounters greater air resistance |