Question 1

Which of the following has the effect of reducing the gravitational force between two objects?

Accepted Answer

The gravitational force between two objects decreases as the distance between them increases, according to Newton's law of universal gravitation.

Question 2

The figure shows the moon orbiting around Earth. Suppose that the force of gravity between Earth and moon suddenly "switched off." Which of the three arrows point in the direction that the moon would move after gravity vanished?

Accepted Answer

The moon would continue moving in the direction of its velocity at the moment gravity vanished, which is tangent to its orbit. Arrow A represents this tangential direction.

Question 3

As the moon circles Earth, the net force on it is

Accepted Answer

The net force on the moon is directed inward toward Earth due to gravitational attraction, which keeps the moon in its orbit.

Question 4

Our sun will conclude its life as

Accepted Answer

The sun will eventually become a white dwarf after it has expanded into a red giant and shed its outer layers. It does not have enough mass to become a black hole or a neutron star.

Question 5

NASA satellites stay up because

Accepted Answer

Satellites stay in orbit because they are moving at a high speed that allows them to continuously "fall" around the Earth, balancing gravitational pull with their forward motion.

Question 6

When you are in a high- flying jet plane, does either your weight or your mass differ from their normal value as measured on the ground?

Accepted Answer

Your mass remains unchanged because mass is a measure of the amount of matter in an object and does not depend on location. However, your weight, which is the force of gravity acting on your mass, is slightly reduced at high altitudes because the gravitational force decreases with distance from the Earth's center.

Question 7

A philosopher informs you that you do not have any free will, because Newtonian physics predicts that the physical universe and everything in it behaves in a deterministic fashion, just like the workings of a clock. A good argument against this position is that

Accepted Answer

Newtonian physics is not applicable in all situations, especially at quantum levels where indeterminacy is observed, and it is challenging to scientifically prove broad philosophical claims about free will.

Question 8

Suppose that the force of gravity between the sun and Earth suddenly stopped operating. What would happen?

Accepted Answer

Without the gravitational force from the sun, Earth would no longer be pulled into its orbit and would continue moving in a straight line tangent to its orbit at the point where the force stopped, due to its inertia.

Question 9

Which of the following would increase the gravitational force between two objects?

Accepted Answer

Gravitational force increases when the distance between two objects decreases, according to Newton's law of universal gravitation.

Question 10

The figure shows the moon orbiting around Earth. Suppose that the direction of the moon's motion is counter- clockwise. Is any net force exerted on the moon?

Accepted Answer

The answer of The figure shows the moon orbiting around...

Question 11

Which one [or ones] of the following is a possible final state for a star that has come to the end of its "lifetime" by running out of fuel and then gravitationally collapsing?

Accepted Answer

A star can end its life as a black hole, white dwarf, or neutron star, depending on its initial mass.

Question 12

Suppose Earth collapsed down to one- tenth of its present radius, while retaining all of its present mass. Compared to your present mass, your mass would be

Accepted Answer

Mass is an intrinsic property of matter and does not change with the size or shape of the object.

Question 13

Astronauts, in satellites orbiting Earth, feel weightless. Are they really weightless?

Accepted Answer

The answer of Astronauts, in satellites orbiting Earth, feel weightless....

Question 14

An important similarity that Newton noticed between a falling apple and the moon was that

Accepted Answer

Newton observed that both the falling apple and the moon experience a force directed towards the center of the Earth, which results in their accelerations also being directed towards the center of the Earth.

Question 15

If you weighed 800 newtons on Earth, how much would you weigh at 6000 km [one Earth radius] above the surface of Earth?

Accepted Answer

The gravitational force decreases with the square of the distance from the center of the Earth. At 6000 km above the surface, you are at twice the Earth's radius, so the weight is (1/2^2) = 1/4 of the original weight, which is 200 newtons.

Question 16

A space satellite weighs 100,000 newtons on Earth. When orbiting at a height of 6000 km [one Earth- radius] above Earth, its weight is

Accepted Answer

The gravitational force decreases with the square of the distance from the center of the Earth. At 6000 km above the Earth, the distance is doubled (2 Earth radii), so the weight is reduced to one-fourth, making it 25,000 newtons.

Question 17

Today, we know that Newton's "laws" are

Accepted Answer

Newton's laws are not accurate for molecular-sized objects, as quantum mechanics provides a more accurate description at that scale.

Question 18

We now know that Newtonian physics is not valid [i.e., not correct] for

Accepted Answer

Newtonian physics is not valid for very fast-moving objects, as it does not account for the effects of relativity, which become significant at speeds close to the speed of light.

Question 19

You hold an apple in one hand and an orange in the other. If you doubled the mass of the apple and tripled the mass of the orange, without changing the distance between them, the gravitational force between them would be

Accepted Answer

The gravitational force between two objects is proportional to the product of their masses. If the mass of the apple is doubled and the mass of the orange is tripled, the product of their masses becomes six times larger, thus increasing the gravitational force by a factor of six.

Question 20

If you somehow increased Earth's radius, without changing its mass, would this affect your weight?

Accepted Answer

Your weight would decrease because gravitational force depends on the distance from the center of the Earth. Increasing Earth's radius increases this distance, reducing the gravitational force and thus your weight.

Quiz 5: Newtons Universe