3.1.5 Weight

Question 1

Weight

Answer 1

• Mass and weight are not the same thing. Mass is the amount of material an object contains and weight is the force of gravity exerted on it, W = mg .
• When an object is not moving the force of gravity is always balanced by an opposing force.

Question 2

A 50 kg woman stands on a bathroom scale. The woman and the scale sit on top of a 30 kg box, which, in turn, is on top of a second bathroom scale. Everything rests inside an elevator that is falling with a constant acceleration of 2 m / s2. What reading will each scale show? The mass of each scale is 3 kg. Use 10 m / s2 as the acceleration due to gravity on the Earth’s surface.

Answer 2

Scale 1 = 400 N

Scale 2 = 664 N

Question 3

If re  is the radius of the Earth, how far above the surface of the Earth would you have to go so that your true weight is one-fourth of what it is on the surface of the Earth?

Answer 3

re

Question 4

A person weighing 600 N (mass = 60 kg) when at rest stands on a scale inside a train. The train begins to accelerate horizontally at a rate of 3.5 m / s2. What reading will the scale then give for the weight of the person? Use 10.0 m / s2 as the acceleration due to gravity on the Earth.

Answer 4

600 N

Question 5

True or false?
If the Earth shrank in size, but all other factors remained the same, all of its satellites, including the Moon, would fly off into space.

Answer 5

false

Question 6

Which of the following is the most reasonable explanation of why astronauts float (i.e., are apparently weightless) inside a space shuttle in a circular orbit around the Earth?

Answer 6

The space shuttle is pulled toward the Earth and accelerates downward at a rate equal to the acceleration of gravity, therefore causing an apparent weight of zero.

Question 7

An object with a mass of 10 kg sits on top of a bathroom scale inside an elevator. If the elevator begins to accelerate upward at a rate of 3 m / s2, what reading will the bathroom scale yield for the weight of the object? Use 9.8 m / s2 for the acceleration of gravity on the Earth’s surface.

Answer 7

128 N

Question 8

Suppose you carve out a small region exactly at the Earth’s center and stand inside that region. What would you weigh? Assume the Earth is a perfect sphere and has a uniform density.

Answer 8

0

Question 9

Weightlessness occurs ____________.

Answer 9

in a deep, remote region of space, far from other objects