CP Review Sheet

CP Review Sheet Newton’s Laws

1. An apple that has a mass of 0.10 kg has the same mass wherever it is. The amount of matter that makes up the apple (depends on, does not depend on) the location of the apple. It has the same resistance to acceleration wherever it is – its inertia everywhere is (the same, different). The weight of the apple is a different story. It may weigh exactly 1.0 N in San Francisco and slightly less in mile-high Denver, Colorado. On the surface of the moon the apple would weigh 0.17 N and far out in outer-space it may have almost no weight at all. The quantity that does not change with location is (mass, weight). The quantity that may change with location is its (mass, weight). That’s because (mass, weight) is a measure of gravitational force on a body, and this force varies with distance. So we see that weight is the force of gravity between two bodies, usually some small object in contact with the earth. When we refer to the (mass, weight) of an object, we are usually speaking of the gravitational force that attracts it to the earth.

2. A. Mathematically state the relationship that defines acceleration: ______

B. Mathematically state the relationship that defines how acceleration is produced ______

3. Two people with the same mass of 50.0 kg are riding in a pickup truck at 20 m/s. They are brought to an abrupt stop in a head-on collision with a drunk driver who has crossed the divider line. One person wears a seat belt and is brought to a stop in 0.10 s. The other is not wearing a seatbelt and is brought to a halt by the dashboard in 0.01s.

A. What is the deceleration of the person who comes to a stop wearing the seat belt? Remember the equation for acceleration from a prior unit!

B. How much average force is exerted by the seat belt to bring the first person to a stop?

C. What is the deceleration of the person who comes to a stop by hitting the dashboard? Use the acceleration equation again

D. How much average force is exerted by the dashboard on the person?

4. In what direction does friction act with respect to the motion of a sliding object?

5. The Law of Inertia states that no force is required to maintain motion. Why, then do you have to keep peddling on your bicycle to maintain motion? 6. An elephant and a mouse would both have the same weight – zero – in gravitational free space. If they were moving toward you with the same speed would they bump into you with the same effect? ______Explain.

7. Two closed containers look the same, but one is packed with lead and the other with a few feathers. How could you determine which had more mass if you and the containers were orbiting in a weightless condition in outer space?

8. What is meant by the net force that acts on an object?

9. If the forces exerted on an object are 50.0 N in one direction and 30.0 N in the opposite direction, what is the net force exerted on the object?

10. A cart is being moved by a certain net force. If the net force is doubled, how much does the acceleration change?

11. A cart is being moved by a certain net force. If a load is dumped into the cart so its mass is doubled, how much does the acceleration change?

12. How much air resistance acts on a 100 N bag of nails that falls at its terminal velocity?

13. If you hit a wall with a force of 200 N, how much force is exerted on you?

14. In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant?

Why does the vertical component of the velocity of the projectile change? 15. Neglecting air resistance, if you throw a ball straight upward with a speed of 20 m/s, how fast will it be moving when you catch it?

16. At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and drops to the ground. If air resistance can be neglected, which ball – the one dropped from rest or the one thrown - strikes the ground first?

17. For the following, tell whether the statement matches Newton’s 1st , 2nd, or 3rd Law.

______a. Things tend to keep on doing what they’re doing!

______b. When the road is covered with ice, cars tend to keep going in a straight line rather than making a curve! ______c. Using aluminum instead of steel makes it possible to trim 477 pounds off of a typical 3500 pound car. The less the weight (or mass) of a car, the less fuel it takes to make it go! ______d. One reason it is so painful to stub your toe against a rock is that the rock hits you back!

______e. For every action there is an equal and opposite reaction.

______f. Forces tend to accelerate objects while mass tends to resist acceleration.

______g. Boxers often experience hemorrhaging because their brain slams into their skull repeatedly during matches. ______h. Whiplash may occur when sitting in a car which is hit from behind, especially if headrests aren’t in place. ______i. F = ma

______j. Law of Acceleration

______k. action - reaction

______l. It takes more force to accelerate a Mack Truck than a Toyota.

______m. Forces always occur in pairs.

______n. An astronaut pushed out of a spacecraft will continue moving in a straight line at a constant speed forever (or until an unbalanced force acts on her.) ______o. If you blow up a balloon and release it, the balloon flies away

______p. The football player who needs to move the fastest is often the smallest member of the team.

______q. While you are running through the woods, your toe is stopped by a root and you fall forward – not backward. ______r. Paul is sitting watching a movie. When the movie is over it is hard for him to get up and leave. ______s. Seat belts are a necessary safety feature in moving passenger vehicles.

______t. When you step off of the boat onto the dock, the boat moves away from the dock slightly. 18. The following statements are FALSE. Change the incorrect term to make the statement correct! a. It would be just as hard to lift a car on the moon as it is to lift the same car on earth. b. A baseball bat hits a ball with a force of 100 pounds. The bat slows down a bit because the ball exerts a resisting force against the bat of more than 100 lbs. c. A bullet is fired straight down from the top of a high cliff. Neglecting air resistance, the acceleration of the bullet is more than 9.8 m/s/s. d. The acceleration of an object is directly proportional to its mass. e. A ball falling form a great height will reach terminal speed when the force of the air resistance equals its mass. f. Newton’s third law deals with two forces acting on one object. g. If a light object and a heavy one are dropped together in a vacuum, the heavy object will hit bottom first. h. When an object is at rest, its inertia tends to make it move. i. If there is no net force acting on an object, its motion will be one with increasing acceleration. j. Assume that you are driving down a straight road at constant speed. A small ball is tied on the end of a string hanging from the rear view mirror. When you apply the brakes, the ball will swing backward. k. The newton is the unit for mass in the metric system.

19. What is the mass of a woman who weighs 300 Newtons?

20. What is the mass of an object accelerated at a rate of 15.0 m/s/s if the applied net external force is 82.5 newtons?

21. Which car experiences the greater force?

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