Question 1

Which of the following statements correctly distinguishes between mass and weight?

Accepted Answer

Mass is a measure of the amount of matter in an object, while weight is the gravitational force acting on that mass.

Question 2

A 100 kg astronaut is standing on the surface of Mars, where the acceleration due to gravity is $$g_{Mars} = 3.71\ \mathrm{m/s^2$}. $$What is the astronaut's weight on Mars?

Accepted Answer

$$w = 371\ \mathrm{N}$$

Question 3

Near the surface of the Earth, the acceleration due to gravity $$g is $$given by which formula?

Accepted Answer

$$g = \dfrac{GM_E}{r_E^2$}$$

Question 4

A box of mass $$m$$ rests on a horizontal table. What is the magnitude of the normal force $$N$$ exerted by the table on the box?

Accepted Answer

$$N = mg$$

Question 5

A 65-kg woman stands on a scale in an elevator that accelerates downward at $$0.20g. $$What does the scale read during this acceleration?

Accepted Answer

Question 6

A block of mass $$m is $$placed on a roof inclined at $$30^\circ to $$the horizontal. What is the component of the block's weight perpendicular to the roof?

Accepted Answer

$$mg \cos 30^\circ$$

Question 7

If a block slides down a frictionless incline at $$30^\circ$$, what is its acceleration?

Accepted Answer

$$a = g \sin 30^\circ$$

Question 8

In low Earth orbit (about 300 km above the surface), the weight of a 100 kg astronaut is reduced by about 10% compared to their weight on the surface. Which formula correctly calculates their weight in orbit?

Accepted Answer

$$w = m \left( \dfrac{GM_E}{(R_E + h)^2$} \right)$$

Question 9

Which statement about the normal force $$N$$ and the weight $$w of an $$object on a flat surface is correct?

Accepted Answer

They are equal in magnitude but act on the same object and are not Newton's third law pairs.

Question 10

A box of mass $$m is at $$rest on an incline at angle $$	heta. $$What is the normal force $$N$$ exerted by the incline on the box?

Accepted Answer

$$N = mg \cos 	heta$$

Question 11

Which of the following best describes the direction of the gravitational field $$\vec{g}$$ near Earth's surface?

Accepted Answer

Downward, toward the center of the Earth

Question 12

Two boxes, A and B, are connected by a light cord and pulled horizontally with a force $$F. If $$box A has mass $$m_A$$ and box B has mass $$m_B$$, what is the acceleration $$a of $$the system?

Accepted Answer

$$a = \dfrac{F}{m_A + m_B}$$

Question 13

Which of the following is true about the tension in an ideal (massless, non-stretching) cord connecting two masses?

Accepted Answer

The tension is the same at every point along the cord.

Question 14

A 100 kg astronaut is in low Earth orbit (300 km above the surface). If $$R_E = 6400\ \mathrm{km}$$ and $$g = 9.8\ \mathrm{m/s^2$} at $$the surface, what is the approximate acceleration due to gravity at this altitude?

Accepted Answer

$$g_{orbit} \approx 8.9\ \mathrm{m/s^2$}$$

Question 15

When solving dynamics problems using Newton's laws, which forces should be included in the free-body diagram for an object?

Accepted Answer

All forces acting ON the object

Question 16

A block of mass $$m is $$placed on a frictionless incline at angle $$	heta. If no $$other forces act, what is the net force causing the block to accelerate down the incline?

Accepted Answer

$$mg \sin 	heta$$

Question 17

Which of the following is a correct statement about Newton's third law pairs?

Accepted Answer

They are always equal in magnitude and opposite in direction, acting on different objects.

Question 18

If the net force on an object is zero, what can be said about its acceleration?

Accepted Answer

Its acceleration is zero.

Question 19

A chandelier is suspended from the ceiling by a chain. What is the force exerted by the ceiling on the chain?

Accepted Answer

Equal to the weight of the chandelier

Gravitational Force, Weight, and Normal Force: Study Notes

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