physics vocabulary

30) Mike performed 5 J of work in 10 secs. Joe did 3 J of work in 5 secs. Who produced the greater power?

1) Mike produced more power 2) Joe produced more power 3) both produced the same amount of power

25) In a baseball game, the catcher stops a 90-mph pitch. What can you say about the work done by the catcher on the ball?

1) catcher has done positive work 2) catcher has done negative work 3) catcher has done zero work

10) 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

9) 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.

4) 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

3) 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.

12) What does "centripetal" mean?

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

16) 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.

14) 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.

5) 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

18) A 1000-kg car and a 2000-kg car are hoisted the same distance in a gas station. Raising the more massive car requires

A) less work. B) as much work. C) twice as much work. D) four times as much work. E) more than four times as much work. Answer: C Diff: 1

17) When an object is lifted 10 m, it gains a certain amount of potential energy. If the same object is lifted 20 m, its potential energy gain is

A) less. B) the same. C) twice as much. D) four times as much. E) more than four times as much.

Which requires more work: lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m?

A) lifting the 50-kg sack B) lifting the 25-kg sack C) Both require the same amount of work.

19) An object that has kinetic energy must be

A) moving. B) falling. C) at an elevated position. D) at rest. E) A& B

1) 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.

15) 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

26) You and your friend both solve a problem involving a skier going down a slope, starting from rest. The two of you have chosen different levels for y = 0 in this problem. Which of the following quantities will you and your friend agree on?

A) skier's PE B) skier's change in PE C) skier's final KE 1) only B 2) only C 3) A, B, and C 4) only A and C 5) only B and C

11) An object that has potential energy may have this energy because of its

A) speed. B) acceleration. C) momentum. D) location.

8)When a car is braked to a stop, its kinetic energy is transformed to

A) stopping energy. B) potential energy. C) energy of motion. D) energy of rest. E) heat.

2) 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

13) 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.

21) What is the magnitude and direction of the gravitational force that acts on a person who weighs 500 N at the earth's surface?

Answer: 500 N straight downward: the weight of the person.

22) Toss a rock at an angle into the air and it follows a curved path. Its velocity at any instant can be resolved into horizontal and vertical components. Which of these components changes with time, and why?

Answer: Only the vertical component changes with time because it is in the same direction as Earth's gravity. Going upward, the rock is going against gravity and its upward component of velocity decreases. Downward, the vertical component increases as gravity increases the speed of the rock. But the horizontal component is neither with nor against gravity. No force acts sidewise (barring air drag), which is why there is no change in the horizontal component of velocity.

20) Earth and the Moon gravitationally attract each other. Does the more massive Earth attract the Moon with a greater force, the same force, or less force than the Moon attracts Earth? What reasoning guides your answer?

Answer: The force between each is the same, in accord with Newton's Third Law. Note also from Newton's formula for gravitation that the force does not depend on the order of the masses, but depends simply on the product.

23) Why do satellites remain in orbit while the force of gravity pulls downward on them?

Answer: They remain in orbit because the force of gravity pulls perpendicular to the motion of the satellite. With no component of force in the direction of motion, no change in speed occurs—only a change in direction.

24)Why does the force of gravity do no work on a bowling ball rolling along a bowling alley?

Answer: Work is done on an object only when a force, or some component of a force, acts in the direction of motion of the object. In the case of the bowling ball, the force of gravity is perpendicular to the motion with no component parallel to the alley. (We will see later that, for the same reason, the force of gravity does no work on satellites in circular orbit.)

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

True False