Q: Which forces should appear on the free-body diagram for Box 1, held by a hand and attached to a string?

$$f_{\text{hand,1}},\ n_{\text{hand,1}},\ T_{\text{rope,1}},\ w_{\text{earth,1}}$$

Q: What is the maximum angle $$\theta$$ before the box starts to slide, in terms of the static friction coefficient $$\mu_s$$?

$$\theta = \tan$$^{-1}$$(\mu_s)$$

Q: If the box is sliding down the incline, what is the expression for its acceleration?

$$a = g (\sin \theta - \mu_k \cos \theta)$$

Question 1

Refer to the velocity vs. time graph shown. What is the acceleration of the object between $$t = 1\ 	ext{s}$$ and $$t = 3\ 	ext{s}$$?

Accepted Answer

$$+1.0\ 	ext{m/s}^2$$

Question 2

Using the velocity vs. time graph, what is the total displacement of the object from $$t = 0\ 	ext{s} to$$ $$t = 6\ 	ext{s}$$?

Accepted Answer

$$+8.0\ 	ext{m}$$

Question 3

A child throws a ball straight upward from a height of $$1.2\ 	ext{m}$$ above the ground. The ball lands after $$0.95\ 	ext{s}. $$What is the average velocity of the ball during its flight?

Accepted Answer

$$-2.3\ 	ext{m/s}$$

Question 4

A ball is thrown upward and lands on the ground. What is the velocity of the ball just before it lands?

Accepted Answer

$$-5.9\ 	ext{m/s}$$

Question 5

A squirrel runs $$5.0\ 	ext{m}$$ west in $$4.0\ 	ext{s}$$, then $$3.0\ 	ext{m}$$ north in $$16\ 	ext{s}. $$What is the magnitude of its average velocity?

Accepted Answer

$$0.29\ 	ext{m/s}$$

Question 6

A dart is launched at $$21.0\ 	ext{m/s} at$$ $$35^\circ$$ above the horizontal. How long does it take to travel $$5.0\ 	ext{m}$$ horizontally?

Accepted Answer

$$0.42\ 	ext{s}$$

Question 7

In a head-on car collision, which object is the passenger’s head most likely to hit first, and which part of the brain is most likely to be injured first?

Accepted Answer

Frontal airbag and front of the brain

Question 8

You step onto a scale in an elevator. Which statement about the gravitational force and normal force is correct?

Accepted Answer

They never constitute an action–reaction pair.

Question 9

If the elevator is moving downward and speeding up with an acceleration of $$0.50\ 	ext{m/s}^2$$, what is the normal force exerted by the scale on a $$65\ 	ext{kg}$$ person?

Accepted Answer

$$600\ 	ext{N}$$

Question 10

A kitten falls from a window. At $$15\ 	ext{m/s}$$, what is its apparent weight? (mass $$2.0\ 	ext{kg}$$, drag coefficient $$1.1$$, area $$0.050\ 	ext{m}^2$$, air density $$1.2\ 	ext{kg/m}^3)$$

Accepted Answer

$$7.4\ 	ext{N}$$

Question 11

What is the terminal speed of the kitten? (mass $$2.0\ 	ext{kg}$$, drag coefficient $$1.1$$, area $$0.050\ 	ext{m}^2$$, air density $$1.2\ 	ext{kg/m}^3)$$

Accepted Answer

$$24\ 	ext{m/s}$$

Question 12

Which forces should appear on the free-body diagram for Box 1, held by a hand and attached to a string?

Accepted Answer

$$f_{	ext{hand,1}},\ n_{	ext{hand,1}},\ T_{	ext{rope,1}},\ w_{	ext{earth,1}}$$

Question 13

For a box of mass $$m$$ resting on an incline at angle $$	heta$$, what is the magnitude of the frictional force if the box is not sliding?

Accepted Answer

$$f_s = m g \sin 	heta$$

Question 14

What is the maximum angle $$	heta$$ before the box starts to slide, in terms of the static friction coefficient $$\mu_s$$?

Accepted Answer

$$	heta = 	an$$^{-1}$$(\mu_s)$$

Question 15

If the box is sliding down the incline, what is the expression for its acceleration?

Accepted Answer

$$a = g (\sin 	heta - \mu_k \cos 	heta)$$

Question 16

A person moves toward a motion detector with increasing speed. Which velocity vs. time graph best represents this motion?

Accepted Answer

A straight line with negative slope starting below zero and decreasing

Question 17

A cart rolls from rest down an incline, then continues on a flat surface. Which speed vs. time graph best represents its motion?

Accepted Answer

A linearly increasing segment followed by a horizontal segment

Question 18

Two blocks of masses $$m_1$$ \u003c $$m_2$$ are pushed up a smooth incline at constant speed. Is the net force acting on the smaller block greater than, less than, or equal to the net force acting on the larger block?

Accepted Answer

Equal, because both have zero acceleration

Step-by-Step Guidance for Phys 114 Practice Midterm Exam 1 (Kinematics, Dynamics, and Forces)

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