Q: A block is pulled with a force at an angle of $$30^\circ$$ above the horizontal. If the force is $$50 \ \mathrm{N}$$ and the block moves $$3 \ \mathrm{m}$$ horizontally, what is the work done by the force?

$$W = 50 \times 3 \times \cos 30^\circ = 130 \ \mathrm{J}$$

Question 1

A 5 kg box is pulled across a horizontal surface with a constant force of 20 N. If the coefficient of kinetic friction between the box and the surface is 0.2, what is the acceleration of the box? (Assume $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 1.2 \ \mathrm{m/s^2$}$$

Question 2

Which of the following statements about Newton's Third Law is correct?

Accepted Answer

The action and reaction forces are equal in magnitude and opposite in direction.

Question 3

A car rounds a flat curve of radius 50 m at a speed of 20 m/s. What is the magnitude of the required centripetal force if the car has a mass of 1000 kg?

Accepted Answer

$$F_c = 4000 \ \mathrm{N}$$

Question 4

A tennis ball and a bowling ball are dropped from the same height. Ignoring air resistance, which statement is true about their accelerations?

Accepted Answer

Both balls accelerate at the same rate due to gravity.

Question 5

A block slides down a frictionless incline of height $$h. $$What is its speed at the bottom, using the work-energy principle?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 6

Which equation correctly represents Newton's Second Law in component form for the x-direction?

Accepted Answer

$$F_x = m a_x$$

Question 7

A 10 kg object is at rest on a horizontal surface. What is the normal force acting on it?

Accepted Answer

$$N = 98 \ \mathrm{N}$$

Question 8

A force of $$\vec{F} = 3\hat{i} + 4\hat{j} N $$moves an object by $$\Delta \vec{r} = 2\hat{i} + 1\hat{j} m. $$What is the work done by the force?

Accepted Answer

$$W = 11 \ \mathrm{J}$$

Question 9

Which of the following is NOT a type of force commonly included in free-body diagrams?

Accepted Answer

Centripetal force

Question 10

A 2 kg object moves in a circle of radius 0.5 m at a constant speed of 4 m/s. What is the centripetal acceleration?

Accepted Answer

$$a_c = 8 \ \mathrm{m/s^2$}$$

Question 11

If a force acts at an angle $$	heta to $$the direction of displacement, the work done by the force is given by:

Accepted Answer

$$W = F \Delta x \cos 	heta$$

Question 12

A block is pulled with a force at an angle of $$30^\circ$$ above the horizontal. If the force is $$50 \ \mathrm{N}$$ and the block moves $$3 \ \mathrm{m}$$ horizontally, what is the work done by the force?

Accepted Answer

$$W = 50 	imes 3 	imes \cos 30^\circ = 130 \ \mathrm{J}$$

Question 13

Which of the following best describes an object in equilibrium?

Accepted Answer

The net force acting on it is zero.

Question 14

A 3 kg object is pushed with a force of 15 N. What is its acceleration?

Accepted Answer

$$a = 5 \ \mathrm{m/s^2$}$$

Question 15

Which of the following is the correct expression for kinetic energy?

Accepted Answer

$$KE = \frac{1}{2}mv^2$

Question 16

A student decomposes a vector $$\vec{A}$$ into its x- and y-components. If $$|\vec{A}| = 10$$ and it makes a $$60^\circ$$ angle with the x-axis, what is $$A_x$$?

Accepted Answer

$$A_x = 10 \cos 60^\circ = 5$$

Question 17

A 2 kg object is moving at 3 m/s. What is its kinetic energy?

Accepted Answer

$$KE = 6 \ \mathrm{J}$$

Question 18

Which of the following is true about static friction?

Accepted Answer

Static friction can be less than or equal to $$\mu_s N.$$

Question 19

A Ferris wheel rotates at constant speed. Which statement is true about the net force acting on a passenger?

Accepted Answer

The net force points toward the center of the circle.

Dynamics in One Dimension and Work-Energy Principles

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