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physics 1310 > exam 2 > Flashcards

exam 2 Flashcards

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1
Q

A 60 W incandescent light bulb and a 6 W led both give off the same light. Compare the cost of burning a 60 W incandescent light bulb to the cost of burning a 6 W led light bulb for 24 hours.

A

The LED is 10 times cheaper because it uses 10 times less energy

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2
Q

A wheel rotates with an angular speed of 3 radians per second and it has a radius of 2 meters. What is the linear speed of a bug located on the outer radius is this wheel?

A

6 m/s

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3
Q

the power expended doing 100 J of work in 50 s is

A

2 W

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4
Q

When a twirling ice skater brings her arms inward, her rotational speech

A

increases

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5
Q

In considering the work energy theorem, the work done on an object by a net force is always

A

equal to the objects change in kinetic energy

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6
Q

On a rotating turntable, how do tangential speed and rotational speed vary with distance from the center?

A

tangential speed increases with distance, rotational speed is constant

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7
Q

a 2-kg ball is held 4 m above the ground. relative to the ground its potential energy is

A

80 J

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8
Q

Two objects have the same mass and radius. One is a hoop and the other is a solid cylinder. If you race the two objects down an incline neglecting air resistance, which do you expect to reach the bottom of the incline first?

A

the solid cylinder because it has a lower rotational inertia and so it will have the greater acceleration

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9
Q

Freddy Frog drops vertically from a tree onto a horizontally moving skateboard. The skateboard slows. Which of the following are reasons for this?

A
  • the momentum is conserved, so now with the extra mass on the board the velocity will be less
  • adding Freddy’s mass increases the force of friction
  • Freddy will cause additional air resistance as he adds to the frontal surface area in the direction of motion
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10
Q

tidal friction is causing

A

the earth to slow its rotation rate very, very gradually

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11
Q

a same-size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater

A

momentum

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12
Q

which of the following is NOT true in regard to centrifugal force?

A

centrifugal force is a real force that pulls outward on an object that is undergoing circular motion

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13
Q

consider a satellite in an elliptical orbit about earth. which of the following is NOT true?

A

the speech of the satellite is greatest when it is farther from earth

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14
Q

an astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will

A

move in the opposite direction at a lower speed

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15
Q

the rotational inertia of an object is greater when most of the mass is located

A

away from the rotational axis

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16
Q

when the distance between two stars decreases by one-third, the force between them

A

increases to nine times as much

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17
Q

a ball rolling down an incline has its maximum potential energy at

A

the top

18
Q

a stationary 200 kg person is initially holding 50 kg ball while standing on a skateboard. the person throws he ball to the right, and the ball moves with a speed of 12 m/s. the person on the skateboard

A

moves to the left with a speed of 3 m/s

19
Q

why do we only see one side of the moon which is the “man in the moon” face of the moon?

A

we only see one side because tidal effect have slowed is rotation rate until it is already tidally locked in a synchronous orbit

20
Q

a bicycle that travels four as fast as another when braking to stop will skid

A

sixteen times as far

21
Q

which of the following is a unit of work?

A

joule

22
Q

a seesaw is balanced with the fulcrum at its midpoint. If a 3 kg weight is placed one meter from the fulcrum on one side, where would you need to place a 6 kg weight on the opposite side in order to balance the seesaw again?

A

one half meter from the fulcrum

23
Q

a 2 kg rifle that is suspended by strings fires a .01 kg bullet at 200 m/s. the recoil velocity of the rifle is about

A

1 m/s

24
Q

a light aluminum ball and heavy lead ball of the same size roll down an incline. when they are halfway down the incline, they will have the same

A

none

25
Q

you exert a 50 N force on one end of a simple lever and move this end of the lever down half a meter. the other end exerts a 100 N force upward and moves an object resting there

A

one quarter of a meter

26
Q

In Einsteins theory of gravitation, we understand the gravitational field as

A

a warping of space time by a massive object

27
Q

how does the greenhouse effect work? what is the physics?

A

the sun warms the ground, which causes the ground to radiate in infra-red wavelengths that are strongly absorbed by carbon dioxide and other green house gases, causing the lower atmosphere to warm

28
Q

what does it mean for a gas to be green house gas?

A

the gas is in the atmosphere and it strongly absorbs infrared radiation

29
Q

a 1 kg rock is suspended from the tip of a horizontal meter stick at the 0/cm mark so that the meter stick barely balances like a seesaw when its fulcrum is at the 25/cm mark. from this information, the mass of the meter stich is

A

1 kg

30
Q

a simple machine like a pulley can do all of the following except

A

create energy

31
Q

a 5000 kg freight car moving at 2 m/s collides with a 10,000 kg freight care at rest. they couple upon collision and move away at

A

2/3 m/s

32
Q

a possible way for a black hole to be created in nature is that

A

a massive star must collapse until the escape velocity at the event horizon becomes so large light cannot escape

33
Q

if a ping pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the ping pong ball must be

A

more than the golf ball

34
Q

the famous leaning tower of pisa doesn’t topple over because its center of gravity is

A

above a place of support

35
Q

an object that has kinetic energy must be

A

moving

36
Q

if you exert a net torque on an object you will find that

A

the object may speed up or slow down its rotation rate

37
Q

a firecracker bursts while freely falling. the combined momentum of its fragments

A

equals the momentum of the firecracker at the time of burst

38
Q

which of the following are considered greenhouse gases

A

carbon dioxide and water vapor

39
Q

the work done in pushing a TV set a distance of 2 m with an average force of 20 N is

A

40 J

40
Q

NASA has more than a dozen space probes orbiting the earth keeping tabs on changes in our climate. what have these probes discovered

A
  • they have found that sea level is rising and global temperature is rising
  • they have found that artic sea ice is being lost at a rate of 13% each decade
  • they have found that carbon dioxide content in the atmosphere is higher that and any time in the last 1 million years

physics 1310 (17 decks)

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