Deck 6: Gravity, Projectiles, and Satellites

Question 1

Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them

A) remains constant.
B) decreases.
C) increases.
D) increases, then decreases.
E) decreases, then increases.

Answer 1

increases.

Question 2

A hunter on level ground fires a bullet at an angle of 10 degrees above the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground
First?

A) the fired one
B) the dropped one
C) Both hit at the same time.

Answer 2

the dropped one

Question 3

A woman on the surface of the Earth has a mass of 50 kilograms and a weight of 490 newtons. If the woman were floating freely inside a space habitat far away from Earth, she would have

A) less weight and more mass.
B) more weight and less mass.
C) less weight and the same mass.
D) less weight and less mass.
E) none of these

Answer 3

less weight and the same mass.

Question 4

The speeds of the planets about the sun depend on

A) their periods of rotation.
B) the masses of the planets.
C) their distances from the sun.
D) None of the above are correct.

Question 5

Minimal orbital speed about the Earth is about 8 km/s. Minimal orbital speed about the moon would be

A) more than 8 km/s.
B) less than 8 km/s.
C) about 8 km/s.

Question 6

Inside a freely-falling elevator, there would be no

A) apparent weight for you.
B) gravitational force on you.
C) both of these
D) none of these

Question 7

A very massive object A and a less massive object B move toward each other under the influence of gravitation. Which force, if either, is greater?

A) the force on B
B) the force on A
C) Both forces are the same.

Question 8

The concept of force is not fundamental to

A) Newton's theory of gravitation.
B) Einstein's theory of gravitation.
C) both of these
D) neither of these

Question 9

Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are

A) without support forces.
B) beyond the main pull of Earth's gravity.
C) above the Earth's atmosphere.
D) all of these
E) none of these

Question 10

A weight watcher who normally weighs 400 N stands on top of a very tall ladder so she is one Earth radius above the Earth's surface. How much would she weigh there?

A) 100 N
B) 400 N
C) 200 N
D) 0
E) none of these

Question 11

A "weightless" astronaut in an orbiting shuttle is

A) like the shuttle, pulled by Earth's gravitation.
B) shielded from the Earth's gravitational field.
C) beyond the pull of gravity.
D) pulled only by gravitation to the shuttle which cancels the Earth's gravitational pull.
E) none of these

Question 12

Minimal orbit speed about the Earth is about 8 km/s. Minimal orbital speed about Jupiter would be

A) about 8 km/s.
B) more than 8 km/s.
C) less than 8 km/s.

Question 13

A stone is thrown horizontally from the top of a cliff. One second after it has left your hand its vertical distance below the top of the cliff is

A) 15 m.
B) 5 m.
C) 10 m.

Question 14

Two objects move toward each other because of gravity. As the objects get closer and closer, the acceleration of each

A) increases.
B) remains constant.
C) decreases.

Question 15

A satellite describes an elliptical orbit about a planet. The satellite travels much faster when it is directly over a

A) great plain or plateau.
B) large island.
C) high mountain range.
D) large ocean.
E) None of the above choices affects its speed very much.

Question 16

Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 degrees and the other at 60 degrees. The projectile to hit the ground first will be the one
Fired at (neglect air resistance)

A) 30 degrees.
B) 60 degrees.
C) Both hit at the same time.

Question 17

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, its vertical component of velocity.

A) increases
B) decreases
C) remains unchanged

Question 18

What prevents satellites such as a space shuttle from falling?

A) the absence of air drag
B) gravity
C) Nothing; they're falling continuously all around the Earth.

Question 19

If the sun somehow became twice as massive, your weight as normally measured here on earth would

A) double.
B) not change.
C) quadruple.

Question 20

How far must one travel to get away from the Earth's gravitational field?

A) to a region beyond the solar system
B) to a region well beyond the moon
C) to a region above the Earth's atmosphere
D) Forget it; you can't travel far enough.

Question 21

A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m down range. What is the player's
Pitching speed?

A) about 25 m/s
B) about 20 m/s
C) about 5 m/s
D) about 10 m/s
E) none of these

Question 22

When you step on a weighing scale at noon, the Earth pulls you down and the overhead sun pulls you upward. The reason the sun's pull doesn't decrease your weight at noon is because

A) the weighing scale is calibrated only in Earth weight.
B) the sun's pull is cancelled by the gravitation of other celestial bodies.
C) of tidal effects in the "solid" Earth.
D) you, the scale, and the Earth are freely falling around the sun.
E) the sun's pull on you is negligibly small.

Question 23

Acceleration due to gravity on the moon is less than on Earth, and the moon is smaller than Earth. So compared to an Earth satellite, a satellite in close orbit about the moon would travel

A) faster.
B) the same.
C) slower.
D) Not enough information is given to say.

Question 24

A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in

A) more than 0.5 s.
B) 0.5 s.
C) less than 0.5 s.

Question 25

The tangential velocity of an Earth satellite is its velocity

A) parallel to the surface of the Earth.
B) attributed to satellites moving in any direction.
C) perpendicular to the surface of the Earth.

Question 26

The fastest moving planet in a solar system is

A) the most massive planet.
B) the planet nearest the sun.
C) the smallest planet.
D) the planet farthest from the sun.
E) any planet, for they all move at the same speed.

Question 27

A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because

A) the net force acting on it is zero.
B) it is not acted on by any forces.
C) it is not acted on by any horizontal forces.
D) it has no vertical component of velocity to begin with.
E) none of these

Question 28

A rocket coasts in an elliptical orbit about the Earth. To attain escape velocity using the least amount of fuel in a brief firing time, should it fire off at the apogee, or at the perigee? (Hint: Let "Fd
= change in KE" guide your thinking.)

A) perigee, where it is closest and fastest
B) apogee, where it is farthest and slowest
C) same either location

Question 29

An asteroid exerts a 360-N gravitational force on a nearby spacecraft. This force is directed

A) toward the asteroid.
B) toward the sun.
C) away from the asteroid.

Question 30

Without air resistance, a projectile fired horizontally at 8 km/s from atop a mountain will

A) return later to its starting position and repeat its falling behavior.
B) accelerate downward at g as it moves horizontally.
C) trace a curve that matches the earth's curvature.
D) all of these
E) none of these

Question 31

If a satellite's radial velocity is zero at all times, its orbit must be

A) circular.
B) parabolic.
C) elliptical.
D) geosynchronous.

Question 32

If the Earth's mass decreased to one-half its original mass with no change in radius, then your weight would

A) decrease to one half your original weight.
B) stay the same.
C) decrease to one quarter your original weight.
D) none of these

Question 33

The factor most directly responsible for making a black hole invisible is its

A) color.
B) mass.
C) surface escape velocity.
D) size.
E) none of these

Question 34

An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is

A) nearest the Earth.
B) farthest from the Earth.
C) It travels at constant speed everywhere in orbit.

Question 35

Consider a monkey wrench released at rest at the far edge of the solar system. Suppose that it drops to the Earth by virtue of only Earth gravity. It will strike the Earth's surface with a speed of about

A) 9.8 m/s.
B) 11 km/s.
C) 8 km/s.
D) the speed of light.

Question 36

What is the force of gravity on a 500-newton woman standing on the Earth's surface?

A) 50 N
B) 500 N
C) 5000 N
D) 250 N
E) none of these

Question 37

The radial velocity of an Earth satellite is its velocity

A) parallel to the surface of the Earth.
B) attributed to satellites moving in any direction.
C) perpendicular to the surface of the Earth.
D) none of these

Question 38

Acceleration is greater for a satellite when it is at the

A) perigee.
B) apogee.
C) zenith.
D) same acceleration at all of the above places

Question 39

Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity

A) increases.
B) decreases.
C) remains constant.

Question 40

A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude. The supplier should

A) disregard altitude because it makes no difference.
B) buy at a high altitude and sell at a low altitude.
C) buy at a low altitude and sell at a high altitude.

Question 41

A bullet fired horizontally from a rifle begins to fall

A) as soon as it leaves the barrel.
B) after air friction reduces its speed.
C) neither of these

Question 42

Half way to the center of a planet of uniform density, your weight compared to at the surface would be

A) one-quarter.
B) one-half.
C) three-quarters.
D) the same as at the surface.
E) zero.

Question 43

An object is placed exactly halfway between the Earth and moon. The object will fall toward the

A) moon.
B) Earth.
C) neither of these

Question 44

If a block is set sliding on a huge frictionless plane in contact with the Earth, it will NOT continue to move at constant speed because

A) gravity will pull in a non-perpendicular direction as the block gets farther out on the plane.
B) of its inertia.
C) gravity gets weaker as distance increases.
D) it is not free from the shackles of Earth's gravity.

Question 45

Consider two planets in space that gravitationally attract each other. If the masses of both planets are doubled, and the distance between them is also doubled, then the force between them is

A) twice as much.
B) one quarter.
C) four times as much.
D) half as much.
E) none of these

Question 46

A projectile is fired vertically from the surface of the Earth at 8 km/s. The projectile will

A) go into circular orbit about the Earth.
B) escape from the Earth.
C) rise and fall back to the Earth's surface.
D) follow an uncertain path.

Question 47

A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, its horizontal component of velocity

A) increases.
B) decreases.
C) remains unchanged.

Question 48

The planet Jupiter is about 300 times as massive as Earth, yet on its surface you would weigh only about 3 times as much. This is because

A) your mass is 100 times less on Jupiter.
B) you are 100 times more weightless there.
C) Jupiter is significantly farther from the sun.
D) Jupiter's radius is 10 times the Earth's radius.
E) none of these

Question 49

When the distance between two stars decreases by half, the force between them

A) increases to four times as much.
B) decreases by one-quarter.
C) decreases by one-half.
D) increases to twice as much.
E) stays the same.

Question 50

The period of a satellite, the time it takes for a complete revolution, depends on the satellite's

A) weight.
B) mass.
C) radial distance.
D) all of these
E) none of these

Question 51

The reason the moon does not crash into the Earth is that the

A) moon has less mass than the Earth.
B) Earth's gravitational field is weak at the moon.
C) gravitational pull of other planets keeps the moon up.
D) moon has a sufficient tangential speed.
E) none of these

Question 52

A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later?

A) 98
B) 490
C) 50 m
D) 100
E) none of these

Question 53

Each of us weighs a tiny bit less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper. The reason for this is the

A) mass of the building attracts us upward slightly.
B) gravitational field is shielded inside the building.
C) both of these
D) none of these

Question 54

A satellite near the Earth makes a full circle in about an hour and a half. How long would a satellite located as far away as the moon take to orbit the Earth?

A) about 28 days
B) the same hour and a half
C) less than an hour and a half
D) More information about the satellite is needed.
E) none of these

Question 55

A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

A) the fired one
B) the dropped one
C) Both hit at the same time.

Question 56

The force of gravity acting on you will increase if you

A) stand on a planet with a radius that is shrinking.
B) burrow deep inside the planet.
C) both of these
D) none of these

Question 57

If you drop a stone into a hole drilled all the way to the other side of the Earth (neglect the molten core), the stone will

A) speed up until it reaches the other side of the Earth.
B) come to an abrupt stop at the center of the Earth.
C) speed up until it gets to the center of the Earth.
D) slow down until it reaches the center.

Question 58

If the radius of the Earth somehow decreased with no change in mass, your weight would

A) not change.
B) increase.
C) decrease.

Question 59

A rocket fired vertically at 11.2 km/s will escape the Earth. If it is instead fired horizontally at this speed, free from obstructions, will it still escape the Earth?

A) No
B) Yes
C) There's no way to tell.

Question 60

A long perfectly level, frictionless bowling alley, over 2000 meters long, is built by a group of students as a class project. The center just touches the earth near their school and the ends of the
Alley extend into outer space. A bowling ball released at one of the ends, starts rolling towards the center of the alley and will continue moving

A) until it strikes the pins at the far end and stops.
B) forever.
C) for a while but slows to a stop before reaching the pins.

Question 61

An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, its acceleration will be

A) 0 g.
B) 1 g upward.
C) 1 g downward.
D) larger than 1 g.
E) none of these

Question 62

What prevents satellites such as the space shuttle from falling?

A) centrifugal force
B) gravity
C) the absence of air drag
D) centripetal force
E) Nothing; they are continually falling as they orbit the Earth.

Question 63

When a star collapses to form a black hole, its mass

A) increases.
B) remains the same.
C) decreases.

Question 64

Our moon travels the fastest as it orbits the Earth when it is

A) performing an eclipse.
B) closest.
C) rotating.
D) revolving.
E) All of the above choices are true.

Question 65

From Earth, one satellite appears to overtake another. The faster satellite is

A) lower.
B) higher.
C) smaller.
D) can't say

Question 66

After a rock thrown straight up reaches the top of its path and then falls a short distance, its acceleration is (neglect air resistance)

A) less than when it was at the top of its path.
B) greater than when it was a the top of its path.
C) the same as it was at the top of its path.

Question 67

A lunar month is about 28 days. If the moon were closer to the Earth than it is now, the lunar month would be

A) unchanged at 28 days.
B) more than 28 days.
C) less than 28 days.

Question 68

The force of gravity does work on a satellite when it is in

A) elliptical orbit.
B) circular orbit.
C) both of these
D) neither of these

Question 69

A projectile is fired vertically from the surface of the Earth at 5 km/s. The projectile will

A) rise and fall back to the Earth's surface.
B) go into circular about the Earth.
C) go into an elliptical orbit about the Earth.
D) none of these

Question 70

Which would require the greater energy; slowing down of the orbital speed of the Earth so it crashes into the sun, or speeding up the orbital speed of the Earth so it escapes the sun?

A) slowing down
B) same each way
C) speeding up

Question 71

For the astronauts inside the orbiting space shuttle, there is no force of Earth gravity acting on them. This statement is

A) sometimes true while in orbit.
B) always true while in orbit.
C) always false.

Question 72

Inside a freely-falling runaway elevator, your

A) apparent weight is zero.
B) acceleration is zero.
C) gravitational interaction with the Earth is zero.
D) all of these
E) none of these

Question 73

Compared to the period of satellites in orbit close to the Earth, the period of satellites in orbit far from the Earth is

A) shorter.
B) the same.
C) longer.
D) not enough information

Question 74

The ground speed of an airplane that has an airspeed of 200 km/h when it is in a 200-km/h crosswind is

A) 200 km/h.
B) 283 km/h.
C) 0 km/h.
D) 1600 km/h.
E) 400 km/h.

Question 75

The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground as others. These twice-as-high apples, for the same mass, have

A) 1/2 the weight.
B) 1/4 the weight.
C) practically the same weight.

Question 76

According to Newton, the greater the masses of interacting objects, the

A) less the gravitational force between them.
B) greater the force between them by the square of the masses.
C) greater the gravitational force between them.

Question 77

The amount of gravitational force that acts on the space shuttle while in orbit is

A) the same as the shuttle's weight on the Earth's surface.
B) nearly zero.
C) almost as much as the shuttle's weight on the Earth's surface.

Question 78

A projectile is fired into the air at an angle of 50 degrees with the ground and lands on a target that is at the same level at which the projectile started. It will also land on the target if it is fired at an angle of

A) 55 degrees.
B) 40 degrees.
C) 45 degrees.
D) 60 degrees.
E) none of these

Question 79

According to Newton, doubling the distance between two interacting objects

A) divides by 2 the gravitational force between them.
B) divides by 4 the gravitational force between them.
C) multiplies by 2 the gravitational force between them.
D) multiplies by 4 the gravitational force between them.

Question 80

A bullet is fired horizontally with an initial velocity of 300 m/s from a tower 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is about

A) 500 m.
B) 400 m.
C) 600 m.
D) 300 m.
E) 200 m.