Download Newton`s Laws…Conceptually

Forces and Newton’s Laws…Conceptually
1. The law of inertia states that no force is required to maintain motion. Why, then, do you have to
keep pedaling your bicycle to maintain motion?
2. If you were in a spaceship and launched a cannonball into frictionless space, how much force
would have to be exerted on the ball to keep it going?
3. Does a 2-kilogram rock have twice the mass of a 1-kilogram rock? Twice the inertia? Twice the
weight (when weighed in the same location)?
4. An elephant and a mouse would both have zero weight in gravity-free space. If they were moving
toward you with the same speed, would they bump into you with the same effect? Explain.
5. How does the tension in your arms compare when you let yourself dangle motionless by both arms
and by one arm?
6. A clothesline is under tension when you hang from it. Why is the tension greater when the
clothesline is strung horizontally then when it hangs vertically?
7. When a junked car is crushed into a compact cube, does its mass
change? Its volume? Its weight?
8. If an elephant were chasing you, its enormous mass would be very threatening. But if you
zigzagged, the elephant’s mass would be to your advantage. Why?
9. When you compress a sponge, which quantity changes: mass, inertia, volume, or weight?
10. What is the cause of friction, and in what direction does it act with respect to the motion of a
sliding object?
11. All other things being equal, why does a heavy skydiver have a terminal speed greater than a light
skydiver? What can be done so that the terminal speeds are equal?
12. What is the difference between saying that one quantity is proportional to another and saying it is
equal to another?
13. A rocket launched from its launching pad not only picks up speed, but its acceleration also
increases significantly as firing continues. Why is this so? (Hint: About 90% of the mass of a
newly launched rocket is fuel.)
14. As a skydiver falls faster and faster through the air (before reaching the terminal speed), does the
net force on her increase, decrease, or remain unchanged? Does her acceleration increase,
decrease, or remain uncharged? Defend your answers.
15. What will be the acceleration of a skydiver when air resistance is half the weight of the skydiver?
16. When you jump up, the world really does coil downward. Why can’t this motion of the world be
noticed?
Forces and Newton’s Laws…Conceptually
17. How can a rocket be propelled above the atmosphere where there is no air to “push against”?
18. In order to increase its speed, why must the horse push harder against the ground than it pulls on
the wagon?
19. If you walk on a long that’s floating in the water, the log moves backward. Why?
20. If a bicycle and a massive truck have a head on collision, upon which vehicle is the impact force
greater? Which vehicle undergoes the greater change in its motion? Defend your answers.
21. Your teacher challenges you and your best friend to each pull on a pair of scales attached to the
ends of horizontal rope, in tug-of-war fashion, so that the readings on the scales will differ. Can
this be done? Explain.
22. Differentiate between rotation and revolution.
23. Distinguish between linear speed and rotational speed.
24. When you whirl a can at the end of a string in a circular path, what is the direction of the force that
acts on the can?
25. If the string from the previous question breaks, what causes the can to move in a straight line path –
centripetal force, centrifugal force or a lack of force? What law of physics supports your answer?
26. Does an inward or an outward force act on the clothes during the spin cycle of a washing machine?
27. If the moon falls, why doesn’t it get closer to the Earth?
28. What is meant by tangential velocity?
29. If you lose your grip on a rapidly spinning merry-go-round and fall off, in which direction will you
fly?
30. While driving North on I-75 at 65 mph you hit a bug that had an initial velocity
of 7.8 mph South. After the collision, what is the approximate velocity of the bug?
How does the force of the bug on the car compare to the force of the car on the
bug? How does the acceleration, as a result of the collision, of the car compare to
the acceleration of the bug?
31.