The centripetal force that keeps the Earth in its orbit around the sun is provid

Question

The centripetal force that keeps the Earth in its orbit around the sun is provided By inertia By the Earth's rotation on its axis By the gravitational pull of the sun By the sun's rotation on its axis When will your apparent weight be greatest, as measured by a scale in a moving elevator; when the elevator Accelerates downward Accelerates upward Is in free fall Moves at a constant speed Two cars have the same mass, but one is moving three times as fast as the other car is. How much more work will be needed to stop the faster car? the same amount Twice as much, Three times as much Nine times as much Suppose a planet has a mass that is 3 times the mass of the Earth, but the radius is the same as the radius of the Earth. The determine the acceleration of gravity at the surface of the planet, (in m/s^2) 88.2 1.09 29.4 3.27

Explanation / Answer

1. (C) by the gravitational pull of the sun. Gravity is a force of attraction between masses. It provides centripetal force needed to keep a planet in orbit around a star such as Sun.

2. (B) accelerates upwards. The inertia of the person would prefer to stay stationary, so the elevator floor and the scale must push up on the person to accelerate him upward along with the elevator. The scale therefore has to push upward with extra force on the person to accelerate the person's mass upward. This results in greater contact force between the scale and the person. Therefore the normal force is larger, so the reading on the scale is a number that is GREATER than the true weight. FN is the number that we read off the scale. FN=mg+ma, which is greater than the true weight.

4. (C) g/g' = (M/r2)/(3M/r2) = 1/3

9.81/g' = 1/3

g' = 9.81×3 = 29.43 m/s2

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