Q: A 2 kg object is suspended from a rope and is at rest. What is the tension in the rope?

$T = 2\ \mathrm{kg} \times 9.8\ \mathrm{m/s^2} = 19.6\ \mathrm{N}$

Q: A 3 kg object is on the surface of Mars, where $g = 3.7\ \mathrm{m/s^2}$. What is its weight on Mars?

$W = 3 \times 3.7 = 11.1\ \mathrm{N}$

Question 1

Which of the following statements best describes Newton's First Law of Motion?

Accepted Answer

An object at rest remains at rest and an object in motion continues in motion with constant velocity unless acted upon by a net external force.

Question 2

A 5 kg box is at rest on a frictionless surface. If a constant force of 20 N is applied horizontally, what is the acceleration of the box?

Accepted Answer

$a = \frac{20}{5} = 4\ \mathrm{m/s^2}$

Question 3

Which of the following is NOT a fundamental field force?

Accepted Answer

Normal force

Question 4

A spring scale reads 10 N when a downward force $F_1$ is applied. If a second equal force $F_2$ is applied in the same direction, what will the scale read?

Accepted Answer

$30\ \mathrm{N}$

Question 5

Which of the following best describes an inertial frame of reference?

Accepted Answer

A frame moving with constant velocity relative to an inertial frame.

Question 6

A 2 kg object is suspended from a rope and is at rest. What is the tension in the rope?

Accepted Answer

$T = 2\ \mathrm{kg} 	imes 9.8\ \mathrm{m/s^2} = 19.6\ \mathrm{N}$

Question 7

Which of the following is true about mass?

Accepted Answer

Mass is a scalar quantity and is independent of the method used to measure it.

Question 8

A crate of mass 10 kg is pulled across a frictionless floor by a rope with tension $T = 50\ \mathrm{N}$. What is the acceleration of the crate?

Accepted Answer

$a = \frac{50}{10} = 5\ \mathrm{m/s^2}$

Question 9

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

Accepted Answer

$F_x = m a_x$

Question 10

A person pushes a box with a force of 30 N to the right, while friction exerts a force of 10 N to the left. What is the net force acting on the box?

Accepted Answer

$F_{net} = 30\ \mathrm{N} - 10\ \mathrm{N} = 20\ \mathrm{N}$

Question 11

Which of the following statements about weight is correct?

Accepted Answer

Weight is the gravitational force exerted on an object and varies with location.

Question 12

A 3 kg object is on the surface of Mars, where $g = 3.7\ \mathrm{m/s^2}$. What is its weight on Mars?

Accepted Answer

$W = 3 	imes 3.7 = 11.1\ \mathrm{N}$

Question 13

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 acting on different objects.

Question 14

A person stands on a scale in an elevator accelerating upward at $2\ \mathrm{m/s^2}$. If the person's mass is 70 kg, what is the normal force (scale reading)? (Take $g = 9.8\ \mathrm{m/s^2}$)

Accepted Answer

$N = 70 	imes (9.8 + 2) = 826\ \mathrm{N}$

Question 15

Which of the following is NOT a step in solving problems using Newton's Laws?

Accepted Answer

Include all forces acting on every object in the system.

Question 16

A block is at rest on a table. Which forces act on the block?

Accepted Answer

Both the gravitational force downward and the normal force upward.

Question 17

If two forces $F_1$ and $F_2$ act perpendicularly on an object, what is the magnitude of the resultant force?

Accepted Answer

$F_{res} = \sqrt{F_1^2 + F_2^2}$

Question 18

A lamp of mass 4 kg hangs at rest from a chain. What is the tension in the chain?

Accepted Answer

$T = 4 	imes 9.8 = 39.2\ \mathrm{N}$

Question 19

Which of the following is true about the normal force acting on an object on a surface?

Accepted Answer

It can be greater than, less than, or equal to the gravitational force depending on other forces present.

(CH4) Newton's Laws of Motion: Fundamental Concepts and Applications

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