Deck 5: Gravity

Question 1

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

A)50 N
B)250 N
C)500 N
D)509.8 N
E)none of the above

Answer 1

C

Question 2

Inside a freely falling elevator, there would be no

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

Answer 2

B

Question 3

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

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

Answer 3

B

Question 4

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

A)zero
B)100 N
C)200 N
D)400 N
E)none of the above

Question 5

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

A)increase also.
B)decrease.
C)stay the same.

Question 6

Earth's gravitational field extends

A)only above and beyond Earth's surface and cancels inside Earth.
B)both inside and outside Earth and throughout the entire universe.
C)neither A nor B

Question 7

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

A)Earth.
B)Moon.
C)neither A nor B

Question 8

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)one-quarter the weight.
B)one-half the weight.
C)practically the same weight.

Question 9

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

A)less the gravitational force between them.
B)more the gravitational force between them.

Question 10

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

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

Question 11

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

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

Question 12

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

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

Question 13

Newton discovered

A)gravity.
B)that gravity is universal.
C)neither A nor B

Question 14

If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would

A)be the same.
B)double.
C)quadruple.
D)be eight times as much as now.
E)none of the above

Question 15

If the Sun were twice as massive,

A)its pull on Earth would double.
B)the pull of Earth on the Sun would double.
C)both A and B
D)neither A nor B

Question 16

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

Question 17

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

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

Question 18

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

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

Question 19

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

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

Question 20

The direction of a gravitational field is

A)in the same direction of gravitational attraction.
B)away from the center of gravity of an object.
C)opposite to the direction of gravitational attraction.

Question 21

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

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

Question 22

Throw an object at an angle upward. With no gravity it will follow a straight-line path. But because of gravity, at the end of 1 s, it is

A)5 m below the straight line.
B)10 m below the straight line.
C)15 m below the straight line.

Question 23

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

Question 24

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

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

Question 25

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

Question 26

Where is your gravity detector?

A)in your brain
B)inside your ear
C)on your phone
D)in your chest

Question 27

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

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

Question 28

A bullet fired from a rifle begins to fall

A)as soon as it leaves the barrel.
B)after air friction reduces its speed.
C)neither A nor B

Question 29

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

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

Question 30

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

Question 31

The reason the Moon does not crash into Earth is that

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

Question 32

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

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

Question 33

Where is the center of gravity in a triangle?

A)at the top
B)half-way up from the base
C)one-third up from the base
D)on the base

Question 34

What does "centripetal" mean?

A)false force
B)center-seeking
C)inward pull
D)downward push

Question 35

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

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

Question 36

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

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

Question 37

Who could lean the farthest over a cliff without falling?

A)a five foot tall skinny man
B)a lean elderly person
C)a little girl wearing heavy boots
D)a 6 foot 6 inches tall male body builder

Question 38

Inside a freely falling runaway elevator, your

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

Question 39

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

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

Question 40

A projectile is launched vertically at 50 m/s. If air resistance is negligible, its speed upon returning to its starting point is

A)less than 50 m/s.
B)50 m/s.
C)more than 50 m/s.

Question 41

After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is (neglect air resistance)

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

Question 42

An Earth satellite is simply a projectile freely falling around the Earth.

A)True
B)False

Question 43

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

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

Question 44

If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about

A)1 s.
B)2 s.
C)10 s.
D)20 s.
E)not enough information given

Question 45

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

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

Question 46

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)5 m/s
B)10 m/s
C)20 m/s
D)25 m/s
E)none of the above

Question 47

A hunter aims a rifle at an angle of 10° below the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

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

Question 48

A projectile is launched at an angle of 15° above the horizontal and lands downrange. What other projection angle for the same speed would produce the same downrange distance?

A)30°
B)45°
C)50°
D)75°
E)90°

Question 49

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

A)50 m downrange
B)98 m downrange
C)100 m downrange
D)490 m downrange
E)none of the above

Question 50

Two projectiles are fired at equal speeds but different angles. One is fired at an angle of 30° and the other at 60°. Neglecting air resistance, the projectile to hit the ground first will be the one fired at

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

Question 51

An airplane flies at 40 m/s at an altitude of 50 m. The pilot drops a heavy package, which falls and strikes the ground. Where, approximately, does the package land?

A)beneath the plane
B)400 m behind the plane
C)500 m behind the plane
D)more than 500 m behind the plane
E)none of the above

Question 52

A projectile is thrown into the air at an angle of 50° and lands on a target that is at the same level the projectile started. It will also land on the target if it is thrown at an angle of

A)40°.
B)45°.
C)55°.
D)60°.
E)none of the above

Question 53

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

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

Question 54

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

A)less than 0.5 s.
B)more than 0.5 s.
C)0)5 s.

Question 55

An object is thrown vertically into the air. Because of air resistance, the time for its descent will be

A)longer than the ascent time.
B)shorter than the ascent time.
C)equal to the ascent time.
D)not enough information given to say

Question 56

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

A)go into circular motion about Earth.
B)rise and fall back to Earth's surface.
C)follow an uncertain path.

Question 57

The ground speed of an airplane that has an airspeed of 100 km/h when it is in a 100-km/h crosswind is

A)0 km/h.
B)100 km/h.
C)141 km/h.
D)150 km/h.
E)200 km/h.

Question 58

A ball is thrown upward and caught when it comes back down. Neglecting air resistance, the speed with which it is caught is

A)more than the speed it had when thrown upward.
B)less than the speed it had when thrown upward.
C)the same as the speed it had when thrown upward.

Question 59

If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is about

A)1 s.
B)2 s.
C)10 s.
D)not enough information given

Question 60

A hunter aims a rifle at an angle of 10° above the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?

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

Question 61

earth satellites are typically more than 100 km high so as to be above Earth's

A)atmosphere.
B)gravitational field.
C)both A and B

Question 62

A projectile shot with an initial velocity of 141 m/s at an angle of 45° follows a parabolic path and hits a stationary balloon at the top if its trajectory. The speed it hits the balloon is

A)0 m/s.
B)50 m/s.
C)100 m/s.
D)141 m/s.

Question 63

A ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of

A)20 m.
B)30 m.
C)45 m.
D)depends on the initial horizontal speed of the ball

Question 64

What prevents satellites such as the space shuttle from falling?

A)gravity
B)centripetal force
C)centrifugal force
D)the absence of air drag
E)Nothing, they continually fall all around Earth.

Question 65

Consider an escalator at an angle of 45° above the horizontal that moves with a velocity of 2.0 m/s. The vertical component of its velocity is about

A)0)7 m/s.
B)1)4 m/s.
C)1)6 m/s.
D)2)0 m/s.

Question 66

A projectile is fired vertically from the surface of Earth at 10 km/s. The projectile will

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

Question 67

A "weightless" astronaut in an orbiting shuttle is

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

Question 68

Tangential velocity is velocity

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

Question 69

Two motorcycle stunt drivers, one light and the other much heavier, drive their motorcycles up and off an inclined ramp at identical speeds. They both rise in the air and land downrange. Neglecting air drag, the one to attain the greatest height and greatest range is the

A)light driver.
B)heavy driver.
C)both the same

Question 70

A ball rolls off the edge of a horizontal roof at a velocity of 10 m/s. One second later, the speed of the ball is about

A)10 m/s.
B)14 m/s.
C)16 m/s.
D)20 m/s.

Question 71

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

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

Question 72

Planets would crash into the Sun if it weren't for

A)their tangential velocities.
B)their vast distances from the Sun.
C)the inverse-square law.
D)their relatively small masses.
E)the fact that they are beyond the main gravitation of the Sun.

Question 73

The Earlybird communication satellite hovers over the same point on Earth's equator indefinitely. This is because

A)forces other than Earth's gravity act on it.
B)it pulls as hard on Earth as Earth pulls on it.
C)it is beyond the main pull of Earth gravity.
D)it is kept aloft by ground control.
E)its orbital period is 24 hours.

Question 74

Ignoring air drag, what is the maximum speed that can be given to a horizontally moving tennis ball as it clears the net 1.25 m high to remain within the edge of the court, which is 12.0 m distant?

A)12.0 m/s
B)16.0 m/s
C)24.0 m/s
D)48.0 m/s

Question 75

A satellite in an elliptical orbit travels at constant

A)velocity.
B)speed.
C)acceleration.
D)all of the above
E)none of the above

Question 76

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

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

Question 77

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

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

Question 78

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

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

Question 79

Communications and weather satellites always appear at the same place in the sky. This is because these satellites are

A)beyond the pull of Earth's gravitational field.
B)moving at a speed just short of escape velocity.
C)orbiting Earth with a 24-hour period.
D)stationary in space.
E)none of the above

Question 80

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

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