Deck 3: Gravity and Motion

Question 1

What property summarizes a body's tendency to stay in the state of rest or motion?

A) temperature
B) acceleration
C) pressure
D) inertia
E) volume

Answer 1

inertia

Question 2

Which statement is true about Newton's First law of motion?

A) A body at rest stays at rest unless a force is applied to it.
B) A body in motion stays in motion unless a force is applied to it.
C) A body in motion has the tendency to come to a stop eventually.
D) A body at rest stays at rest unless a force is applied to it and a body in motion has the tendency to come to a stop eventually.
E) A body at rest stays at rest unless a force is applied to it and a body in motion stays in motion unless a force is applied to it.

Answer 2

A body at rest stays at rest unless a force is applied to it and a body in motion stays in motion unless a force is applied to it.

Question 3

While riding a bicycle, if you stop pedaling you will still continue to move forward due to ______.

A) gravity
B) inertia
C) acceleration
D) pressure

Answer 3

inertia

Question 4

Consider a large truck and a small car driving up a straight, steep hill. The truck is moving at 60 miles per hour and the car at 30 miles per hour. Assuming that the speeds are constant, which of the two vehicles experiences a larger net force?

A) the truck
B) the car
C) the same: zero net force

Question 5

A car is moving down a straight, steep hill. By applying the brake, the driver is able to keep the speed of the car constant. Which of the following statements is true in this situation?

A) There is a net force on the car.
B) The net acceleration is negative.
C) There is no net force on the car.
D) The net acceleration is positive.

Question 6

When a bus makes a sudden stop the passengers lurch forward as a consequence of ____ law.

A) Newton's First
B) Kepler's Third
C) Newton's Third
D) Kepler's First

Question 7

What do we call the tendency of a body at rest to remain at rest or a body in motion to remain in motion?

A) gravity
B) the "action-reaction" law
C) the tendency of a person to stay in bed in the morning
D) inertia

Question 8

Galileo hypothesized that a ball rolling along a flat surface with no change in speed would _________.

A) have no net force acting on it
B) accelerate, depending on its mass
C) have a net force acting on it, upward from the surface
D) slow down as it rolled down a slope
E) speed up as it rolled up a slope

Question 9

A magician pulls a tablecloth out from under the settings on a dinner table without disturbing the dishes.This is an example of _________.

A) Newton's First law of motion
B) Newton's Second law of motion
C) Newton's Third law of motion
D) the Hannum-Barnum law
E) Kepler's laws of motion

Question 10

A parachutist jumps out of an airplane and opens her parachute.She then floats downward at a constant rate. Why is she not accelerating?

A) The parachute provides an upward force to balance gravity, so the net force is zero.
B) She is accelerating, but gravity's pull is weak at high altitudes.
C) As she falls, she is weightless and therefore cannot accelerate.
D) The parachute has very little mass, so its inertia is negligible.
E) The parachutist exerts a gravitational pull on Earth that is equal to its pull on her.

Question 11

What is Newton's First law of motion?

A) A body continues in a state of rest or uniform motion in a straight line unless made to change that state by forces acting on it.
B) Force equals mass times acceleration, F=ma.
C) Every mass exerts a force on any other mass that is proportional to the product of the masses divided by the square of the distance between them.
D) When two bodies interact, they create equal and opposite forces on each other.

Question 12

How can we tell that the Moon is held in orbit around Earth by a force?

A) The Moon follows a curved path as it orbits.
B) The Moon's gravity creates tides in Earth's oceans.
C) The Moon is always at the same distance from Earth.
D) One side of the Moon is always facing Earth.
E) Earth's gravitational force pulls inward on the Moon.

Question 13

If you see a body in space that is not moving in a straight line at constant speed, what can you say about it?

A) It must be an artificial satellite.
B) There must be a net force acting on it.
C) It is not subject to any outside forces.
D) None of these choices is correct.

Question 14

When an astronaut experiences weightlessness in space, their mass is

A) zero.
B) the same as on Earth.
C) double than on Earth.
D) becoming lesser and lesser as s/he is going higher.

Question 15

After tying a string to a rock, you twirl the rock around above your head. If the string were to break, what path would the rock follow?

A) The rock will fall down immediately.
B) The rock will complete the circle before falling down.
C) The rock will go in a straight line before falling down.
D) The rock will fly upward.

Question 16

An astronaut in orbit around Earth drops her pen, and it floats gently next to her hand.Why does it not fall to the floor?

A) There is no gravity in space.
B) The gravitational pull is very weak at typical altitudes for orbiting spacecraft.
C) Objects in orbit have no mass.
D) All objects in the spacecraft are falling toward Earth at the same rate.
E) The net force on the pen is zero.

Question 17

In your office, you have a rolling chair and a rolling filing cabinet. The chair weighs 10 pounds, and the filing cabinet weighs 50 pounds (it's partly full). If you push both of them away with about the same strength

A) the chair will accelerate about 25 times as much as the cabinet.
B) the cabinet will accelerate about 25 times as much as the chair.
C) the chair will accelerate about 5 times as much as the cabinet.
D) the cabinet will accelerate about 5 times as much as the chair.
E) both will accelerate about the same.

Question 18

If the net force acting on an object doubles, then the _____ doubles as well.

A) mass
B) acceleration
C) speed
D) velocity

Question 19

Which of the following objects (A-D) are accelerating? A. an object at rest, B. an object in motion in a straight line at a constant speed, C. an object in motion in a straight line with increasing speed, D. an object moving in a circle at constant speed.

A) an object at rest only
B) All but an object at rest
C) an object in motion in a straight line with increasing speed only
D) an object in motion in a straight line with increasing speed and an object moving in a circle at constant speed.

Question 20

An ion engine provides a small but constant force on a spacecraft as it moves from Earth to Pluto. Compare the speed of the spacecraft near the beginning of its journey with its speed as it flies past Pluto.

A) The spacecraft's speed at Pluto is the same as its speed near Earth.
B) The spacecraft's speed at Pluto is slower than its speed near Earth.
C) The spacecraft's speed at Pluto is faster than its speed near Earth.
D) The relative speed cannot be determined with the information given.

Question 21

An ion engine provides a small but constant force on a spacecraft as it moves from Earth to Pluto. Compare the acceleration of the spacecraft near the beginning of its journey with its acceleration as it flies past Pluto.

A) The spacecraft's acceleration at Pluto is the same as its acceleration near Earth.
B) The spacecraft's acceleration at Pluto is slower than its acceleration near Earth.
C) The spacecraft's acceleration at Pluto is faster than its acceleration near Earth.
D) The relative acceleration cannot be determined with the information given.

Question 22

What is Newton's Second law of motion?

A) A body continues in a state of rest or uniform motion in a straight line unless made to change that state by forces acting on it.
B) Every mass exerts a force on any other mass that is proportional to the product of the masses divided by the square of the distance between them.
C) Force equals mass times acceleration, F=ma.
D) When two bodies interact, they create equal and opposite forces on each other.

Question 23

A 200-kg spacecraft is launched to the Moon.While in orbit around the Moon, its weight is ____.

A) zero
B) 200 kg
C) about 1/6^th its weight at Earth
D) The answer depends on how close to the Moon the ship is orbiting

Question 24

A 200-kg spacecraft is launched to the Moon. While in orbit around the Moon, its mass is ____.

A) zero
B) 200 kg
C) about 1/6^th its mass at Earth
D) The answer depends on how close to the Moon the ship is orbiting

Question 25

A 200-kg spacecraft is launched to the Moon.After it has landed on the Moon, its weight is ____.

A) zero
B) 200 kg
C) about 1/6its mass onEarth
D) The answer depends on which side of the Moon the spacecraft landed on

Question 26

A 200-kg spacecraft is launched to the Moon. After it has landed on the Moon, its mass is ____.

A) zero
B) 200 kg
C) about 1/6its mass onEarth
D) The answer depends on which side of the Moon the spacecraft landed on

Question 27

A weather satellite moves at a constant orbital speed around Earth.Is this satellite accelerating?

A) yes, the satellite is accelerating - its speed is constant but its direction is changing.
B) yes, the satellite is accelerating - the force of gravity is pulling it toward the ground.
C) yes, the satellite is accelerating - it is in freefall toward the ground.
D) Yes, the satellite is accelerating - its speed is constant but its direction is changing and yes, the satellite is accelerating - it is in freefall toward the ground..
E) Yes, the satellite is accelerating - its speed is constant but its direction is changing; yes, the satellite is accelerating - the force of gravity is pulling it toward the ground; and yes, the satellite is accelerating - it is in freefall toward the ground, are correct.

Question 28

The recoil experienced when firing a shotgun is a consequence of _____ law.

A) Newton's First
B) Kepler's Third
C) Newton's Third
D) Kepler's First

Question 29

The force that pulls an upward going ball back to Earth and keeps the Moon in its orbit is called _______.

A) inertia
B) gravity
C) pressure
D) escape speed

Question 30

If you double the distance between two bodies, the force of gravity between them would

A) double.
B) become four times as strong.
C) decrease by one half.
D) decrease by one fourth.

Question 31

The Moon is gravitationally attracted to Earth. Is Earth gravitationally attracted to the Moon?

A) Yes, but the force of attraction is less.
B) Yes, and the force of attraction is the same.
C) Yes, but the force of attraction is greater.
D) No, the Moon has no gravity.

Question 32

Which of the following objects is obeying Newton's laws of motion?

A) a sleeping cat
B) a satellite orbiting Earth
C) a runner racing around a track
D) a skydiver falling under the force of gravity
E) All of these choices are correct.

Question 33

Consider an apple falling from a tree. Which of the following apply to this situation?

A) The apple is attracting Earth.
B) Earth is attracting the apple.
C) Earth is attracting the apple; the apple is not attracting Earth.
D) The apple is attracting Earth and Earth is attracting the apple.

Question 34

The gravitational force exerted by the Sun on Earth is ____ the gravitational force exerted by Earth on the Sun.

A) greater than
B) less than
C) equal to
D) unrelated to

Question 35

What is Newton's Third law of motion?

A) When two bodies interact, they create equal and opposite forces on each other.
B) Force equals mass times acceleration, F=ma.
C) Every mass exerts a force on any other mass that is proportional to the product of the masses divided by the square of the distance between them.
D) A body continues in a state of rest or uniform motion in a straight line unless made to change that state by forces acting on it.

Question 36

A diver in midair is pulled toward the pool below by the force of gravity from Earth. Earth experiences an upward force from the diver that ____.

A) is equal to the force on the diver by Earth
B) is less than the force on the diver by Earth
C) is greater than the force on the diver by Earth
D) There is no upward force by the diver on Earth
E) There is insufficient information to determine the gravitational pull on Earth by the diver

Question 37

A bowling ball exerts a force on the pins when it strikes them, knocking them down.The force of the pins on the ball is ____.

A) less than the force of the ball on the pins
B) the same as the force of the ball on the pins
C) larger than the force of the ball on the pins
D) either less or more, depending on how hard the ball is thrown
E) A system of ten bowling pins is too complicated to know the force on the ball

Question 38

A delivery truck and a car collide.Which vehicle experiences the greater force?

A) the truck
B) the car
C) Both the car and the truck experience the same force.
D) We need to know the speed of the truck and the car to find the answer.
E) We need to know the mass of the truck and the car to find the answer.

Question 39

A delivery truck and a car collide.Which vehicle experiences the greater acceleration?

A) the truck
B) the car
C) Both the car and the truck experience the same acceleration.
D) We need to know the speed of the truck and the car to find the answer.
E) We need to know the mass of the truck and the car to find the answer.

Question 40

A rocket in space fires its engines continuously until it runs out of fuel. Describe the motion of the rocket.

A) The rocket's speed increases until its engines stop firing, and then coasts in a straight line.
B) The rocket's speed is a constant value until the engines stop firing, and then coasts to a stop.
C) The rocket's speed increases until its engines stop firing, and then coasts to a stop.
D) The rocket's speed does not change, and it continues to move in a straight line.
E) The rocket does not move, as the engines have nothing to push against.

Question 41

At which place on the Earth will you weigh less?

A) at the equator
B) at the North Pole
C) at the South Pole
D) you weigh the same at all of these places

Question 42

If you are lucky enough to get a chance to visit different planets of our Solar System, which of the following statements will be true?

A) Your weight will change, but your mass will remain the same.
B) Your mass will change, but your weight will remain the same.
C) Both your weight and mass will remain the same.
D) Both your weight and mass will change.

Question 43

Which of the following objects is experiencing Earth's gravitational force?

A) a boat floating in water
B) an airplane taking-off
C) a skydiver falling under the force of gravity
D) All of these choices are correct.
E) Only an airplane taking-off and a skydiver falling under the force of gravity above.

Question 44

Suppose that the Sun started shrinking in size, without losing any mass. What would be the effect of the Sun's change on the orbits of the planets?

A) The orbits would become smaller in size.
B) The orbits would become larger.
C) The orbits would not be affected.
D) The planets would escape.

Question 45

How can we mathematically express Newton's law of gravity? (In the following, F is the force of Gravity, G is a constant; m and M are the masses or two bodies (such as Earth and the Sun); and r is the distance between the centers of mass of the two bodies.)

A) F = GMm/r
B) F = GMm/r²
C) F = GMm/r³
D) F = Gm²M/r²

Question 46

If an object's mass (M) is doubled, the gravitational force between it and other objects will be

A) increased by a factor of 2.
B) increased by a factor of 4.
C) decreased by a factor of 2.
D) decreased by a factor of 4.

Question 47

A satellite is moved from a low orbit to one that is twice as far from Earth.The force of gravity is ____.

A) unchanged
B) decreased by a factor of 2
C) decreased by a factor of 4
D) There is no gravity in space.
E) increased by a factor of 2

Question 48

A satellite is moved from a low orbit to one that is twice as far from Earth.Its weight at its new orbit is ____.

A) unchanged
B) decreased by a factor of 2
C) decreased by a factor of 4
D) There is no gravity in space.
E) increased by a factor of 2

Question 49

A satellite is moved from a low orbit to one that is twice as far from Earth.Its mass at its new orbit is ____.

A) unchanged
B) decreased by a factor of 2
C) decreased by a factor of 4
D) There is no gravity in space.
E) increased by a factor of 2

Question 50

Why does something weigh less on the Moon than on Earth?

A) The farther something is from Earth, the lower its weight.
B) The Moon's lower mass creates a lower force of gravity at its surface.
C) The object's weight is the same on the Moon as it is on Earth.
D) Earth's gravity pulls in the opposite direction as the Moon's, so the net force is reduced.
E) The Moon has no atmosphere to apply a downward force on surface objects.

Question 51

If the force of gravity exerted on the Sun by Earth is the same as the force exerted by Earth on the Sun, why does Earth orbit the Sun, and not the other way around?

A) Earth is less massive, and is accelerated more by the gravitational force and moves faster.
B) Planets, by definition, orbit the Sun, and not the other way around.
C) They each orbit around the geometric center of the system.
D) The combined gravitational forces of all the planets keeps the Sun at the center of the Solar System.
E) None of these choices is correct.

Question 52

What is the average orbital speed of Earth around the Sun? (Note: r = 1.5 × 10¹¹ m and P = 3.16 × 10⁷ s.)

A) about 30 km/s
B) about 4.7 km/s
C) about 9.8 m/s²
D) 365 days
E) 1,000 km/s

Question 53

Newton's modification of Kepler's Third law allows astronomers to determine the _____ of celestial objects.

A) mass
B) period
C) distance
D) acceleration

Question 54

Mars completes one orbit around the Sun in approximately two Earth years. Mars orbits at an average distance to the Sun of about 1.5 AU, and Mars' mass is about 1/10 of Earth's mass. Therefore Mars' orbital speed is _____ the orbital speed of Earth.

A) about 0.8 times
B) 1.5 times larger than
C) about 1/10 of
D) about 3 times

Question 55

If the Moon is suddenly and inexplicably moved to four times its current distance from Earth, its orbital speed ______________________________________.

A) increases by a factor of 2
B) increases by a factor of 4
C) decreases by a factor of 2
D) decreases by a factor of 4
E) is unchanged due to its low mass

Question 56

A planet is discovered at a distance of 1 AU from its parent star with a period of 1 year. How does the star's mass compare to our Sun's?

A) The star has the same mass as the Sun.
B) The star's mass is around 2 times smaller than the Sun's.
C) The star's mass is around 2 times larger than the Sun's.
D) The star's mass is around 4 times smaller than the Sun's.
E) The star's mass is around 4 times larger than the Sun's.

Question 57

A planet is discovered at a distance of 1 AU from its parent star with a period of 2 years. How does the star's mass compare to our Sun's?

A) The star has the same mass as the Sun.
B) The star's mass is around 2 times smaller than the Sun's.
C) The star's mass is around 2 times larger than the Sun's.
D) The star's mass is around 4 times smaller than the Sun's.
E) The star's mass is around 4 times larger than the Sun's.

Question 58

Earth's radius at the equator is larger than that at the poles. Where is Earth's surface gravity more?

A) at the equator
B) at the North and South Poles
C) it is the same everywhere
D) at the top of Mount Everest

Question 59

If a newly discovered planet has four times the mass of Earth, but it still has the same surface gravity as Earth, how big must this new planet be?

A) four times as large as Earth
B) twice as large as Earth
C) the same size as Earth
D) half the size of Earth
E) one fourth of the size of Earth

Question 60

The acceleration of gravity on Earth's surface is 9.8 m/s². What is the acceleration of gravity at a height of 6,400 km above Earth's surface? (Hint: recall the 1/r² dependence and note that Earth's radius is 6,400 km.)

A) 4.9 m/s ²
B) 2.45 m/s ²
C) 19.6 m/s ²
D) 9.8 m/s ²

Question 61

What does surface gravity measure?

A) the tendency of a planet's surface to collapse under gravity
B) how fast an object needs to go to escape a planet's gravity
C) the attraction between the surfaces of two massive objects
D) the gravitational acceleration at a planet's or star's surface

Question 62

Why does a golf ball hit on the Moon travel farther than one hit on Earth? (Neglect air resistance and bad golfers.)

A) The surface gravity is lower on the Moon, so the acceleration of gravity is lower.
B) The mass of the ball is lower on the Moon, so it is accelerated more easily there.
C) The surface gravity is lower on the Moon, so the golf club can be accelerated more easily there.
D) The Moon is physically smaller than Earth, so the golf ball only looks like it travels farther.

Question 63

How are mass and weight different?

A) There is no difference; they are the same.
B) Weight is a measure of how much gravity pulls an object; mass is how much matter the object has.
C) Mass is the amount of matter an object contains; weight is how much mass an object contains.
D) Weight is the amount of matter an object contains; mass is the type of matter an object is made of.

Question 64

If your mass is 60 kilograms on Earth, what is it on the Moon?

A) 0 kilograms, because the Moon has no gravity
B) 60 kilograms, because mass does not depend on gravity
C) 120 kilograms, because the Moon's gravity is greater than Earth's
D) 360 kilograms, because the Moon is a spherical object

Question 65

The surface gravity of Jupiter is only 2.5 times larger than Earth's, despite the fact that Jupiter's mass is more than 300 times that of Earth. How can this be?

A) The radius of Jupiter is much larger than Earth's, so a point in the cloud tops of Jupiter is farther from its center.
B) The radius of Earth is 300 times smaller than the radius of Jupiter.
C) Jupiter is mostly hydrogen and helium, while Earth is mostly iron and rock.
D) Jupiter has no surface, so it does not have a surface gravity.

Question 66

If a barbell weighs 10 pounds on the Moon, what would it weigh on Earth?

A) 1.67 pounds. Surface gravity on the Moon is 1/6 that on Earth.
B) 10 pounds. Gravity is the same on Earth and the Moon.
C) 30 pounds. Surface gravity on Earth is 3 times that on the Moon.
D) 60 pounds. Surface gravity on Earth is 6 times that on the Moon.

Question 67

An astronaut on the Moon drops a feather and a hammer at the same time.Which hits the ground first?

A) The hammer hits first due to its larger mass.
B) The feather hits first due to the decreased weight of the hammer.
C) The feather hits first since there is no air resistance on the Moon.
D) The feather and the hammer hit the ground at the same time.

Question 68

The speed an object needs to move away from the gravitational pull of Earth is called

A) orbital velocity.
B) escape velocity.
C) rotational velocity.
D) random velocity.

Question 69

Suppose that a planet was discovered that has twice the mass and twice the diameter of Earth. What would be the escape velocity for this planet? (Assume that for Earth the escape velocity is 11 km/s.)

A) 22 km/s
B) 11 km/s
C) 15.6 km/s
D) 7.8 km/s

Question 70

What does escape velocity measure?

A) the gravitational attraction at a planet's surface
B) how fast an object needs to go to escape a planet's gravity
C) how far away an object needs to be to escape a planet's gravity
D) how fast an object needs to go to escape hostile space aliens

Question 71

The escape velocity from the Moon is 2.4 km/s. If an astronaut hits a golf ball such that it just reaches this speed, the ball will __________________________.

A) continue moving away from the Moon, never to return
B) follow a very elliptical orbit around the Moon
C) move away from the Moon, but return some time later
D) either orbit the Moon or escape its gravitational pull, depending on the direction the ball is hit

Question 72

An object is moving in a straight line and at a constant speed of 60 kilometers per hour. We therefore conclude that the net force on this object is zero.

Question 73

An object moving on a circle at constant speed is an example of accelerated motion.

Question 74

The reason Earth's moon does not fall into Earth is because it orbits beyond Earth's gravitational pull.

Question 75

Newton's laws of motion apply only to objects experiencing the force of gravity. They do not apply to objects experiencing a magnetic force.

Question 76

By Newton's Third law, Earth's pull on the Moon is equal to the Moon's pull on Earth.

Question 77

Astronomers can determine the mass of the Sun by applying Newton's modification of Kepler's Third law.

Question 78

Larger planets (higher mass) in the solar system have higher orbital speeds because they are attracted more strongly by the Sun.

Question 79

Mars completes one orbit around the Sun in approximately two Earth years. Mars' average distance to the Sun is about 1.5 AU. Therefore the Mars' orbital speed is lower than Earth's orbital speed.

Question 80

It is possible to use Newton's modification to Kepler's Third law to determine the mass of Jupiter's moon, Io.