Lesson 4

Question 1

Which of the following is an example in which you are traveling at constant speed but not at constant velocity?

Answer 1

driving around in a circle at exactly 100 km/hr

Question 2

Momentum is defined as

Answer 2

mass times velocity

Question 3

As long as an object is not gaining or losing mass, a net force on the object will cause a change in

Answer 3

velocity

Question 4

You are standing on a scale in an elevator. Suddenly you notice your weight decreases. What do you conclude?

Answer 4

The elevator is accelerating downwards.

Question 5

The movement of a pool ball, after being struck by a cue, is an example of

Answer 5

Newton’s second law of motion.

Question 6

Changing the orbit of a spacecraft by firing thrusters is an example of

Answer 6

Newton’s third law of motion.

Question 7

What quantities does angular momentum depend upon?

Answer 7

mass, velocity, and radius

Question 8

Which of the following is not a unit of energy?

Answer 8

kilowatt

Question 9

Radiative energy is

Answer 9

energy carried by light.

Question 10

What does temperature measure?

Answer 10

the average kinetic energy of particles in a substance

Question 11

The amount of gravitational potential energy released as an object falls depends on

Answer 11

its mass and the distance it falls

Question 12

According to the universal law of gravitation, the force due to gravity is

Answer 12

inversely proportional to the square of the distance between objects.

Question 13

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will

Answer 13

decrease by a factor of 9.

Question 14

The orbital period of a geosynchronous satellite is

Answer 14

23 hours 56 minutes.

Question 15

According to what we now know from Newton’s laws, which of the following best explains why Kepler’s second law is true?

Answer 15

A planet’s angular momentum must be conserved as it moves around its orbit.

Question 16

Suppose a lone asteroid happens to be passing relatively near Jupiter (but not near any of its moons), following a hyperbolic orbit as it approaches Jupiter. Which of the following statements would be true?

Answer 16

The asteroid’s orbit around Jupiter would not change, and it would go out on the same hyperbolic orbit that it came in on.

Question 17

Imagine we’ve discovered a planet orbiting another star at 1 AU every 6 months. The planet has a moon that orbits the planet at the same distance as our Moon, but it takes 2 months. What can we infer about this planet?

Answer 17

It is less massive than Earth.

Question 18

The energy attributed to an object by virtue of its motion is known as

Answer 18

kinetic energy.

Question 19

Which of the following best explains why the Moon’s orbital period and rotation period are the same?

Answer 19

The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.