# motion

(See attached file for full problem description with diagrams)

1. If an object is moving at a constant velocity, then we can assert that:

a. there must be a force in the direction of the velocity

b. there must be no force in the direction of the velocity

c. there must be no net force

Justify your answer!

2. To tighten the metal head of a hammer, one friend recommends that you drop the hammer with the handle end down and another friend tells you to drop it with the handle end up. Which one would be more effective? Why? Explain in terms of Newton's 1st Law of motion.

3. A catcher stops a 92 mi/h pitch in his glove, bringing it to rest in 0.2 seconds. If the mass of the ball is 0.30 Kg, what is the force exerted by the catcher on the ball?

4. Your groceries are usually placed in a plastic bag. The handles of the bag will tear off if the upward force is greater than 80 N. What is the maximum load (mass) that can be lifted with an acceleration of 1.5 m/s2.

5. A 40 Kg child takes a ride on a Ferris wheel that rotates at a speed of ½ rev. per minute and has a diameter of 18 meters.

a. What is the speed of the child (in m/s)?

b. What is the centripetal acceleration of the child?

c. What forces are acting on the child at the tops of the ride? Can the child ride safely without being restrained?

6. The motion of an object is represented by the following graph:

Describe the motion of the object for the following time intervals:

0 - 15 seconds

15 - 25 seconds

25-35 seconds

35-40 seconds

40-45 seconds

45-50 seconds

6. From the previous graph, calculate the acceleration for the following time intervals:

0 - 15 seconds 25-35 seconds 40-45 seconds

15 - 25 seconds 35-40 seconds 45-50 seconds

7. From the previous graph, calculate the distance traveled by the object for the following time intervals:

0 - 15 seconds 15 - 25 seconds 25-35 seconds

35-40 seconds 40-45 seconds 45-50 seconds

7. In your new job, you are the technical advisor for the writers of a gangster movie about Bonnie and Clyde. In one scene Bonnie and Clyde try to flee from one state to another. (If they got across the state line, they could evade capture, at least for a while until they became Federal fugitives.) In the script, Bonnie is driving down the highway at 108 km/hour, and passes a concealed police car that is 1 kilometer from the state line. The instant Bonnie and Clyde pass the patrol car, the cop pulls onto the highway and accelerates at a constant rate of 2 m/s2.

The writers want to know if they make it across the state line before the pursuing cop catches up with them...will they?

#### Solution Preview

Please see the attached file.

1. If an object is moving at a constant velocity, then we can assert that:

a. there must be a force in the direction of the velocity

b. there must be no force in the direction of the velocity

c. there must be no net force

Justify your answer!

C is correct. The acceleration is zero since the velocity is constant. So according to newton's second law, F=ma, F is zero. But F here is the total force or net force, so C is correct.

2. To tighten the metal head of a hammer, one friend recommends that you drop the hammer with the handle end down and another friend tells you to drop it with the handle end up. Which one would be more effective? Why? Explain in terms of Newton's 1st Law of motion.

You should drop the hammer with the handle end down to tighten the head. According to Newton's first law, the head tends to remain in the state of motion, in this case moving down. By this way the head is tightened.

3. A catcher stops a 92 mi/h pitch in his glove, bringing it to rest in 0.2 seconds. If the mass of the ball is 0.30 Kg, what is the force exerted by the catcher on the ball?

Newton's second law of motion:

The force exerted by the catcher on the ball is 6.132 N.

4. Your groceries are usually placed in a plastic bag. The handles of the bag ...

#### Solution Summary

The solution provides detailed explainations of motion related questions.