## Description

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**PHY-102: Motion Exercises **

Complete the following exercises.

- Jane is collecting data for a ball rolling down a hill. She measures out a set of different distances and then proceeds to use a stopwatch to find the time it takes the ball to roll each distance.
- What is the independent variable in her experiment?
- What is the dependent variable in her experiment?
- Give one control variable for her experiment.

- Consider an experiment where you drop an object.
- Briefly describe your proposed experiment. (Make sure it is controlled).
- What would be the independent variable for your experiment?
- What would be the dependent variable for your experiment?
- Give one control variable for your experiment.

- Consider a freely falling object.
- What is the acceleration (in m/s
^{2}) after 5 seconds of fall? - What is the acceleration (in m/s
^{2}) after 10 seconds of fall? - What is the velocity (in m/s) after 5 seconds of fall?
- What is the velocity (in m/s) of 10 seconds of fall?

- What is the acceleration (in m/s

- A sign is hung between two cables as illustrated below. If the sign weighs 350 N, what is the tension (in N) in each cable?

- A construction worker on a high-rise building is on a platform suspended between two cables as illustrated below. The construction worker weighs 850 N, the plank weighs 450 N, and the tension in the left cable is 550 N.
- What is the tension (in N) in the right cable?
- Explain your answer.

- Two forces of 50 N and 30 N, respectively, are acting on an object. Find the net force (in N) on the object if …
- the forces are acting in the same direction
- the forces are acting in opposite directions.

- A box is pulled straight across the floor at a constant speed. It is pulled with a horizontal force of 48 N.
- Find the net force (in N) on the box.
- Find the force of friction (in N) from the floor on the box.
- The person pulling on the box stops pulling and the box comes to a rest. Find the force of friction (in N) on the box when at rest.

- A bowling ball rolls 32 meters in 0.8 seconds. Find the average speed (in m/s) of the bowling ball in m/s.

- A car accelerates from 3.5 m/s to 17 m/s in 4.5 seconds. Find the acceleration of the car in m/s
^{2}.

- Rank the following from lowest to highest:
- The support force on you standing in an elevator at rest.
- The support force on you standing in an elevator accelerating upward.
- The support force on you standing in an elevator accelerating downward.

- Describe the speed and acceleration of the ball released from the top of the track shown in the figure below.

- Describe the speed and acceleration of the ball released from the top of the track shown in the figure below.

- Describe the speed and acceleration of the ball released from the top of the track shown in the figure below.

- You throw a ball upward with a speed of 14 m/s. What is the acceleration of the ball after it leaves your hand? Ignore air resistance and provide an explanation for your answer.

- How would your answer to the previous question change if you take into account the effects of air resistance?

- Describe the speed and acceleration of a person sky diving. Include in your explanation a description of the motion before the parachute is opened as well as a description of the motion after the parachute is opened.

- A net force of 24 N is acting on a 4.0-kg object. Find the acceleration in m/s
^{2}.

_{ }

- A person pulls horizontally with a force of 64 N on a 14-kg box. There is a force of friction between the box and the floor of 36 N. Find the acceleration of the box in m/s
^{2}. Show your work.

**The remaining questions are multiple-choice questions:**

- One difference between a hypothesis and a theory is that a hypothesis
- is a guess that has not been well tested, whereas a theory is a synthesis of well-tested guesses.
- is testable, whereas a theory is not testable.
- can be revised, whereas a theory cannot be revised.
- is not testable, whereas a theory is testable.

- A car starts from rest and reached a speed of 24 m/s in 6 seconds. What is the acceleration of the car?
- 144 m
- 6 m/s
^{2} - 4 m/s
^{2} - 10 m/s
^{2} - 0 m/s
^{2}

- Which of the following forces is NOT a contact force?
- Friction force
- Support force
- Force of gravity
- Tension force

- If you pull horizontally on a desk with a force of 150 N and the desk doesn’t move, the friction force must be 150 N. Now if you pull with 250 N so the desk slides at constant velocity, the friction force is
- more than 150 N, but less than 250 N.
- 250 N.
- more than 250.

- Suppose a particle is accelerated through space by a constant 10 N force. Suddenly the particle encounters a second force of 10 N in a direction opposite to that of the first force. The particle
- is brought to a rapid halt.
- theoretically accelerates to speeds approaching the speed of light.
- continues at the speed it had when it encountered the second force.
- gradually slows down to a halt.

- Newton’s First Law of Motion applies to
- objects at rest only.
- moving objects only.
- both moving and nonmoving objects.

- A freely falling object starts from rest. After falling for 2 seconds, it will have a speed of about
- 5 m/s
- 10 m/s
- 20 m/s
- 40 m/s

- Suppose an object is in free fall. Each second the object falls
- the same distance as in the second before.
- a larger distance than in the second before.
- with the same instantaneous speed.
- with the same average speed.