Quiz

QUIZ

1. What is one thing that defines a body that is not in equilibrium?

a. A body having acceleration b. A body having velocity c. A body having mass d. A body having potential energy

Answer: a. Any body having acceleration is not in equilibrium; however, a body having velocity, mass, and potential energy may still be in equilibrium.

2. What least affects the torque on an object?

a. The force applied b. The direction of the force c. The starting angle of the object d. The radius from the axis at the center of the object

Answer: c. Torque will depend on the radius from the axis, on the force magnitude and on the direction of the force but not necessarily on the starting angle of the object. Torque involves force that causes rotation of an object on an axis.

3. The pivot point in a diagram is to the far left and the force is pushing upward on the right. What is the direction of torque?

a. It is tangential to the direction of rotation. b. It is toward the center of the axis. c. It is counterclockwise. d. It is clockwise.

Answer: c. The only two choices for torque are clockwise and counterclockwise. In the case described, the torque applied is going to be counterclockwise.

4. How is the direction of torque defined conventionally?

a. Any upward direction for torque is going to be positive. b. Any outward direction for torque is going to be positive. c. Any clockwise direction for torque is going to be positive. d. Any counterclockwise direction for torque is going to be positive.

Answer: d. By convention, torque can be clockwise or counterclockwise. By definition, counterclockwise torque is said to be positive, while clockwise direction for torque is said to be negative.

5. What is considered the advantage of a simple machine?

a. It will decrease the input force necessary to do work. b. It will increase the input force necessary to do work. c. It will do more work than the energy put into it. d. It will do equalize the force output and the force input.

Answer: a. The major advantage of a simple machine is that it will decrease the necessary input force required to do the work of the machine. It cannot do more work than the energy that is put into it because energy is still conserved.

6. The mechanical advantage of a simple machine can be stated in what way?

a. It is the difference between the force input and the force output. b. It is the force input divided by the force output. c. It is the force output divided by the force input. d. It is the energy input minus the work output.

Answer: c. This mechanical advantage is the ratio between the force output and the force input. Higher mechanical advantages happen when the force output is much greater than the force input because of the machine’s ability to take advantage of torque, for example.

7. What is the relationship between the angular acceleration of a rotating system and its tangential acceleration?

a. These two terms are vectors in the same direction as each other and equal in magnitude. b. The tangential acceleration is opposite in direction as angular acceleration but equal in magnitude. c. The tangential acceleration is perpendicular to angular acceleration and is independent in magnitude. d. Tangential acceleration does not have a consistent relationship to the angular acceleration.

Answer: c. The tangential acceleration is perpendicular to angular acceleration and is independent in magnitude.

8. What is the relationship between tangential acceleration, angular acceleration and the radius of the circle being rotated around?

a. The tangential acceleration is directly proportional to the angular acceleration and the radius. b. The tangential acceleration is inversely proportional to the angular acceleration and the radius. c. The tangential acceleration is inversely proportional to the angular acceleration and directly proportional to the radius. d. The tangential acceleration is directly proportional to the angular acceleration and inversely proportional to the radius.

Answer: a. The tangential acceleration is directly proportional to the angular acceleration and directly proportional to the radius. The larger the radius and the larger the angular acceleration, the larger the tangential acceleration.

9. What is true of the velocity of 2 objects of the same mass but of different inertias rolling down a hill?

a. As long as they have the same mass, they will roll down the hill at the same rate. b. The object with a reduced inertia will roll slower down the hill than the object with the greater inertia. c. The object with reduced inertia will spin slower so it travels slower down the hill. d. The object with the reduced inertia will have a greater translational linear velocity down the hill.

Answer: d. High inertias mean that more of the object is involved in rotating or spinning so the energy left over for translational travel is decreased—it will roll down the hill more slowly. Rotational kinetic energy plus translational kinetic energy equals total kinetic energy.

10. If momentum in the linear sense is mass times the velocity, what is the angular momentum of a rotating object?

a. Mass times its angular velocity b. Inertia times its angular velocity c. Mass times its radius times its angular velocity d. Inertia times its linear velocity

Answer: b. Rather than mass, the inertia is used to calculate angular momentum and rather than linear velocity, the angular velocity is used in the equation. Otherwise, the units are the same for both and these are completely analogous to one another.