Q: A 12 kg object is located 1.2 m from a 25 kg object. What is the magnitude of the gravitational force between them? ($$G = 6.67 \times 10$$^{-11}$$\ \mathrm{N\cdot m^2$/kg^2$$}$)

$$1.4 \times 10$$^{-8}$$\ \mathrm{N}$$

Question 1

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

Accepted Answer

An object remains at rest or in uniform motion in a straight line unless acted upon by a net external force.

Question 2

A 10 kg box is pulled across a horizontal surface with a force of 50 N. If the coefficient of kinetic friction between the box and the surface is 0.2, what is the acceleration of the box? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 2.04\ \mathrm{m/s^2$}$$

Question 3

Which of the following is NOT a contact force?

Accepted Answer

Gravitational force

Question 4

A 40 kg sled is sliding on snow with a coefficient of kinetic friction $$\mu_k = 0.05. $$What is the magnitude of the frictional force acting on the sled? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$f_k = 20\ \mathrm{N}$$

Question 5

According to Newton’s Third Law, if you pull on a rope with a force $$\vec{T}$$, what force does the rope exert back on you?

Accepted Answer

$$-\vec{T}$$

Question 6

The SI unit of force is the newton (N). Which combination of base units is equivalent to a newton?

Accepted Answer

$$\mathrm{kg\cdot m/s^2$}$$

Question 7

A block rests on a table. Which force is responsible for supporting the block against gravity?

Accepted Answer

Normal force

Question 8

A car of mass $$1850\ \mathrm{kg} is $$pushed with forces of $$275\ \mathrm{N}$$ and $$395\ \mathrm{N} in $$the $$+x$$ direction, while an opposing force of $$560\ \mathrm{N}$$ acts in the $$-x$$ direction. What is the acceleration of the car?

Accepted Answer

$$0.059\ \mathrm{m/s^2$}$$

Question 9

Which equation correctly expresses Newton’s Law of Universal Gravitation for two masses $$m_1$$ and $$m_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = G\frac{m_1$ m_2$}{r^2$}$$

Question 10

A 12 kg object is located 1.2 m from a 25 kg object. What is the magnitude of the gravitational force between them? ($$G = 6.67 	imes 10$$^{-11}$$\ \mathrm{N\cdot m^2$/kg^2$$}$)

Accepted Answer

$$1.4 	imes 10$$^{-8}$$\ \mathrm{N}$$

Question 11

Which of the following statements about friction is correct?

Accepted Answer

The static frictional force can be greater than the kinetic frictional force.

Question 12

If a block is at rest on a horizontal surface and you gradually increase the applied force, what happens just before the block starts to move?

Accepted Answer

The static frictional force reaches its maximum value.

Question 13

Which of the following is the correct expression for the maximum static frictional force?

Accepted Answer

$$f_{s,\mathrm{max}} = \mu_s N$$

Question 14

A block is in equilibrium on a table. Which of the following must be true?

Accepted Answer

$$\sum F_x = 0$$ and $$\sum F_y = 0$$

Question 15

A 5 kg object is placed on a horizontal surface. If the coefficient of static friction is 0.4, what is the minimum force required to start moving the object? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$14.7\ \mathrm{N}$$

Question 16

Which of the following best describes the normal force?

Accepted Answer

A force perpendicular to the surface that supports the object.

Question 17

A block is pulled by a rope over a frictionless pulley. If the rope is massless and frictionless, what can be said about the tension in the rope?

Accepted Answer

The tension is the same throughout the rope.

Question 18

Which of the following is the correct formula for the weight of an object of mass $$m$$ near the Earth's surface?

Accepted Answer

$$W = m g$$

Question 19

A sled and rider (total mass 40 kg) are sliding on snow with a coefficient of kinetic friction $$\mu_k = 0.05. $$What is the acceleration due to friction? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 0.49\ \mathrm{m/s^2$}$$

Forces and Newton’s Laws of Motion: Structured Study Notes

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