Q: A car moving at 100 km/h comes to a stop with a constant acceleration of $-7.0\ \mathrm{m/s^2}$. What is the stopping distance?

$d = \frac{v_0^2}{2|a|} = \frac{(27.78)^2}{2 \times 7.0} = 55.1\ \mathrm{m}$

Q: A 10 kg object on Earth experiences a gravitational acceleration of $9.8\ \mathrm{m/s^2}$. What is its weight?

$W = m \times g = 10 \times 9.8 = 98\ \mathrm{N}$

Question 1

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

Accepted Answer

An object at rest will remain at rest, and an object in motion will remain in motion at constant velocity unless acted upon by a net force.

Question 2

A 2 kg block is pushed with a net force of 10 N. What is its acceleration?

Accepted Answer

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

Question 3

Which statement correctly distinguishes mass from weight?

Accepted Answer

Mass is a scalar quantity representing the amount of matter, while weight is a vector quantity representing the force of gravity acting on that mass.

Question 4

If a 1 kg object is on Earth and the Moon, which statement is true about its mass and weight?

Accepted Answer

Its mass is the same on both, but its weight is less on the Moon.

Question 5

A car moving at 100 km/h comes to a stop with a constant acceleration of $-7.0\ \mathrm{m/s^2}$. What is the stopping distance?

Accepted Answer

$d = \frac{v_0^2}{2|a|} = \frac{(27.78)^2}{2 	imes 7.0} = 55.1\ \mathrm{m}$

Question 6

Which equation correctly expresses Newton's Second Law in vector form?

Accepted Answer

$\sum \vec{F} = m \vec{a}$

Question 7

A spring stretches 0.2 m when a 4 N force is applied. What is the spring constant $k$?

Accepted Answer

$k = \frac{F}{x} = \frac{4}{0.2} = 20\ \mathrm{N/m}$

Question 8

Which of the following is NOT a common force discussed in Newtonian mechanics?

Accepted Answer

Electromagnetic force

Question 9

A block is pulled to the right with a force of 5 N and experiences a friction force of 2 N to the left. What is the net force?

Accepted Answer

$F_{net} = 5 - 2 = 3\ \mathrm{N}$ to the right

Question 10

Which scientist first proposed that objects tend to remain in motion unless acted upon by a force?

Accepted Answer

Galileo

Question 11

A 10 kg object on Earth experiences a gravitational acceleration of $9.8\ \mathrm{m/s^2}$. What is its weight?

Accepted Answer

$W = m 	imes g = 10 	imes 9.8 = 98\ \mathrm{N}$

Question 12

Which of the following best explains why a moving object eventually comes to rest in the real world?

Accepted Answer

Because forces such as friction and air resistance act to oppose its motion.

Question 13

If the net force on an object is zero, which statement is true?

Accepted Answer

The object moves with constant velocity or remains at rest.

Question 14

Which formula correctly relates density ($\rho$), mass ($m$), and volume ($V$)?

Accepted Answer

$\rho = \frac{m}{V}$

Question 15

A gold bar has a mass of 1.3 lbs and a volume of 0.067 L. What is its density in lbs/L?

Accepted Answer

$\rho = \frac{1.3}{0.067} \approx 19.4\ \mathrm{lbs/L}$

Question 16

Which of the following is a correct unit for force in the SI system?

Accepted Answer

N (newton)

Question 17

A 5 kg object is accelerated at $2\ \mathrm{m/s^2}$. What is the net force acting on it?

Accepted Answer

$F = m 	imes a = 5 	imes 2 = 10\ \mathrm{N}$

Question 18

Which of the following best describes the concept of inertia?

Accepted Answer

The tendency of an object to resist changes in its velocity.

Question 19

A 1 kg mass is weighed on Earth and the Moon. If $g_{Earth} = 9.8\ \mathrm{m/s^2}$ and $g_{Moon} = 1.6\ \mathrm{m/s^2}$, what is the ratio of its weight on Earth to its weight on the Moon?

Accepted Answer

$\frac{W_{Earth}}{W_{Moon}} = \frac{9.8}{1.6} \approx 6.13$

LA_296_Module 3_Forces, Mass, and Newton's Laws: Foundations of Classical Mechanics

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