A rock is thrown straight up in a uniform gravitational field in the absence of

Question

A rock is thrown straight up in a uniform gravitational field in the absence of air resistance. After the rock is thrown and before it is caught, its acceleration A) is upward on the way up and downward on the way down B) is greater on the way down than on the way up C) does not change D) is greater on the way up than on the way down E) is zero at the top but the same non-zero value on the way up as it is on the way down Use the following to answer question 2. 2. A car is slowing down with constant acceleration while traveling westward along a straight road. If the positive direction is defined to be eastward, which graph could represent the position of the car vs. lime? A) none B) ID C) IB D) 1C E) IA 3. Two metal balls are the same size but one weighs twice as much as the other. The balls are dropped from the roof of a single story building at the same instant. The time it lakes the balls lo reach the ground below will be. A) about the same for both balls B) considerably less for the heav ier ball, but not necessarily half as long C) about half as long for the lighter ball as for the heavier one D) considerably less for the lighter ball, but not necessarily half as long E) about half as long for the heavier ball as for the lighter one.

Explanation / Answer

1. For an uniform gravitational field the acceleration is given by:

a = -g it does not change.

Answer: C

2. The car has a constant acceleration so the curve must be a parabolic curve.

The acceleration is in eastward (positive direction) so the curve must be figure 1B

3. The two objetcs have the same acceleration of gravity it does not depend on the mass.

so the answer is A:

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