Q: Which of the following is the correct formula for the dot product of two vectors $$\vec{A}$$ and $$\vec{B} in $$terms of their magnitudes and the angle $$\theta$$ between them?

$$\vec{A} \cdot \vec{B} = AB \cos \theta$$

Question 1

A 2 kg block is pulled across a horizontal surface with a constant force of 10 N. The coefficient of kinetic friction between the block and the surface is 0.2. What is the acceleration of the block? (Assume $$g = 9.8\ \mathrm{m/s^2$}.)$$

Accepted Answer

$$a = 3.04\ \mathrm{m/s^2$}$$

Question 2

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object; weight is the force of gravity acting on that mass.

Question 3

A skydiver reaches terminal speed during free fall. Which of the following statements is true at terminal speed?

Accepted Answer

The magnitude of the resistive force equals the magnitude of the gravitational force.

Question 4

Which of the following is the correct mathematical expression for the gravitational force between two masses $$m_1$$ and $$m_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 5

A 0.5 kg ball is attached to a string and swung in a horizontal circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of the net force acting on the ball?

Accepted Answer

$$F = 4\ \mathrm{N}$$

Question 6

Which of the following best describes a conservative force?

Accepted Answer

A force for which the work done is independent of the path taken, such as gravity or spring force.

Question 7

A box is pushed up a frictionless incline of height $$h$$ and length $$L by a $$constant force parallel to the incline. What is the work done by gravity as the box moves from the bottom to the top?

Accepted Answer

$$W = -mgh$$

Question 8

Which of the following is the correct formula for the dot product of two vectors $$\vec{A}$$ and $$\vec{B} in $$terms of their magnitudes and the angle $$	heta$$ between them?

Accepted Answer

$$\vec{A} \cdot \vec{B} = AB \cos 	heta$$

Question 9

A spring with spring constant $$k = 200\ \mathrm{N/m} is $$compressed by $$0.1\ \mathrm{m}. $$What is the elastic potential energy stored in the spring?

Accepted Answer

$$U = 1\ \mathrm{J}$$

Question 10

Which of the following statements about energy conservation is correct for an isolated system where only conservative forces act?

Accepted Answer

$$E_{\mathrm{mech, initial}} = E_{\mathrm{mech, final}}$$

Question 11

A 60 W light bulb is left on for 2 hours. How much energy does it consume in joules?

Accepted Answer

$$E = 432,000\ \mathrm{J}$$

Question 12

Which of the following is the correct equation for the average power delivered by a constant force $$\vec{F}$$ moving an object through a displacement $$\vec{d} in $$time $$\Delta t$$?

Accepted Answer

$$P_{\mathrm{avg}} = \frac{\vec{F} \cdot \vec{d}}{\Delta t}$$

Question 13

A 3 kg object is dropped from a height of 5 m. Ignoring air resistance, what is its speed just before hitting the ground? (Use $$g = 9.8\ \mathrm{m/s^2$}.)$$

Accepted Answer

$$v = 9.9\ \mathrm{m/s}$$

Question 14

Which of the following is a correct statement about the direction of the gravitational force between two objects?

Accepted Answer

It is always attractive and directed along the line joining the centers of the two masses.

Question 15

A car of mass 1000 kg is moving at 20 m/s. What is its kinetic energy?

Accepted Answer

$$KE = 200,000\ \mathrm{J}$$

Question 16

Which of the following is an example of a non-conservative force?

Accepted Answer

Friction

Question 17

A 5 kg object is moving in a circle of radius 3 m at a constant speed of 6 m/s. What is the magnitude of the net force required to keep it moving in a circle?

Accepted Answer

$$F = 60\ \mathrm{N}$$

Question 18

A 10 kg box is lifted vertically upward at constant speed by a rope for a distance of 2 m. What is the work done by the tension in the rope? (Use $$g = 9.8\ \mathrm{m/s^2$}.)$$

Accepted Answer

$$W = 196\ \mathrm{J}$$

Question 19

Which of the following best describes the direction of a resistive force acting on a moving object?

Accepted Answer

It always acts opposite to the direction of motion.

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