Q: A sleigh is pulled by two snowmobiles with forces $$F_1$$ and $$F_2 at $$angles $$30^\circ$$ and $$\theta to $$the x-axis, respectively. If $$F_1$$/$$F_2 = 1.4$ and the net force points in the x-direction, what is $$\sin \theta$$?

$$\sin \theta = 1.4 \sin 30^\circ$$

Q: If a block is moving up an incline with initial speed $$u$$ and acceleration $$a = -g \sin \theta$$, how long does it take to return to the bottom?

$$t = \frac{2u}{g \sin \theta}$$

Q: Which of the following is a correct vector equation for the net force acting on a body?

$$\vec{F}_{\text{net}} = \sum \vec{F}_i$$

Question 1

According to Newton's First Law, what will happen to an object moving at constant velocity if no net external force acts on it?

Accepted Answer

It will continue moving at constant velocity.

Question 2

A block of mass $$m is $$placed on a frictionless horizontal surface. A force $$F is $$applied horizontally. What is the acceleration $$a of $$the block?

Accepted Answer

$$a = \frac{F}{m}$$

Question 3

Which of the following is NOT a contact force?

Accepted Answer

Gravitational force

Question 4

A sleigh is pulled by two snowmobiles with forces $$F_1$$ and $$F_2 at $$angles $$30^\circ$$ and $$	heta to $$the x-axis, respectively. If $$F_1$$/$$F_2 = 1.4$ and the net force points in the x-direction, what is $$\sin 	heta$$?

Accepted Answer

$$\sin 	heta = 1.4 \sin 30^\circ$$

Question 5

Which statement best describes an inertial reference frame?

Accepted Answer

A frame at rest or moving at constant velocity relative to an inertial frame.

Question 6

A 5 kg block is pulled up a frictionless incline at $$30^\circ$$ with a force $$F$$ parallel to the incline. What is the minimum value of $$F$$ required to just lift the block off the surface?

Accepted Answer

$$F = 5g \sin 30^\circ$$

Question 7

If a person stands on a scale in an elevator accelerating upward with acceleration $$a$$, what does the scale read?

Accepted Answer

$$m(g + a)$$

Question 8

Which of the following best explains why a passenger feels pushed to the side when a car turns sharply?

Accepted Answer

The car is a non-inertial reference frame, and the passenger's inertia resists the change in direction.

Question 9

A block of mass $$m is $$attached to a light, inextensible cord and hangs vertically. What is the tension $$T in $$the cord if the block is at rest?

Accepted Answer

$$T = mg$$

Question 10

Two blocks of masses $$m_1$$ and $$m_2$$ are connected by a light string and pulled by a force $$F on a $$frictionless surface. What is the acceleration $$a of $$the system?

Accepted Answer

$$a = \frac{F}{m_1$ + m_2$}$$

Question 11

Which of the following is a correct statement of Newton's Third Law?

Accepted Answer

For every action, there is an equal and opposite reaction.

Question 12

A 10 kg box is at rest on a horizontal surface. What is the magnitude of the normal force acting on the box?

Accepted Answer

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

Question 13

A block slides down a frictionless incline of angle $$	heta. $$What is its acceleration along the incline?

Accepted Answer

$$a = g \sin 	heta$$

Question 14

Which of the following best describes the mechanical advantage of a machine?

Accepted Answer

The factor by which it multiplies the applied force.

Question 15

A 2 kg object is acted on by a net force of 6 N. What is its acceleration?

Accepted Answer

$$a = 3\ \mathrm{m/s^2$}$$

Question 16

If a block is moving up an incline with initial speed $$u$$ and acceleration $$a = -g \sin 	heta$$, how long does it take to return to the bottom?

Accepted Answer

$$t = \frac{2u}{g \sin 	heta}$$

Question 17

Which of the following is a correct vector equation for the net force acting on a body?

Accepted Answer

$$\vec{F}_{	ext{net}} = \sum \vec{F}_i$$

Question 18

A 3 kg block is suspended by a rope. If the block accelerates upward at $$2\ \mathrm{m/s^2$}$$, what is the tension in the rope?

Accepted Answer

$$T = 3(9.8 + 2) = 35.4\ \mathrm{N}$$

Question 19

Which of the following scenarios best illustrates Newton's Second Law?

Accepted Answer

A car accelerates faster when a greater force is applied to the gas pedal.

Fundamentals of Forces and Newtonian Mechanics

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