PHYS 100 Exam #2

2x the distance= 3x the distance = 8.23x the distance= Half the distance=

4x weaker 9x weaker 67.7x weaker 4x stronger

If you are standing on a scale in an elevator, what exactly does the scale measure? A)your mass B)the force you exert on the scale C)the gravitational force exerted on you by Earth

B)

Inverse

quantity drops with distance

Consider an object of mass 45 kg. Rank the weight of this object at the following locations. Rank from heaviest to lightest. To rank items as equivalent, overlap them.

(heaviest) Jupiter; Earth; Saturn; Mars; Moon (lightest) *Although the weight is different at each location, the mass is the same.

Which of the following elevator situations represents a case of positive acceleration as defined on the previous slide? (1) A. Starting to move up (2) B. Starting to move down (3) C. Coming to a stop moving up (4) D. Coming to a stop moving down (5) E. Moving upward, increasing speed (6) F. Moving downward, decreasing speed (7) G. Moving upward, decreasing speed (8) H. Moving downward, decreasing speed

1, 4, 5, 8

Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________. a)greater than your normal weight at rest b)equal to your normal weight at rest c)less than your normal weight at rest

A) *Increasing speed means acceleration, and when the elevator is accelerating upward you will feel a force pressing you to the floor, making your weight greater than your normal (at rest) weight.

Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________. a)greater than your normal weight at rest b)equal to your normal weight at rest c)less than your normal weight at rest

C) *Even though the elevator is still moving upward, the fact that its speed is slowing means that the acceleration is downward; the situation is rather like that of a ball that is still on its way up after you throw it, even though it is being pulled downward with the acceleration of gravity. Because the acceleration of the elevator is downward, your weight is lower than normal.

As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight? A)The elevator moves upward with constant velocity. B)The elevator moves downward with constant velocity. C)The elevator moves upward while slowing in speed. D)The elevator moves downward while slowing in speed. E)The elevator moves downward while increasing in speed.

D

Square

Drops with the distance square

If you were at the center of the Earth, would the gravitational force on you be more or less than at the surface?

Less than at the surface and equal to zero (a) If you were at the center of the earth, you would gravitationally feel nothing, you would be pulling in every direction

What would be the mass of an object on Jupiter if the object has a mass of 1.7 kg on Mars? Express your answer with the appropriate units.

Mass on Jupiter= 1.7 kg *Mass is an unchanging property of an object that does not depend on gravity.

Inverse Square Law of Gravity

The strength of the gravitational attraction between two objects. Force depends on product of the masses, and inverse square of the distance between masses

What would be the weight of an object on Jupiter if the object weighs 1.7 lb on Mars? Express your answer to two significant figures, and include the appropriate units.

Weight on Jupiter = 11 lb

The now-defunct NASA space shuttles orbited at a height of about 320 km above the ground, which is about 5% of the Earth's radius. Did the astronauts on the shuttle feel weightless?

Yes, because the shuttle was constantly in free fall