On the earth, when an astronaut throws a 0.250-kg stone vertically upward, it returns to his hand a time T later. On planet X he finds that, under the same circumstances, the stone returns to his hand in 2T.
In both cases, he throws the stone with the same initial velocity and it feels negligible air resistance. The acceleration due to gravity on planet X (in terms of g) is
A) g/4.
B) g/2.
C) g/ .
D) g .
E) 2g.
Question 2
A ball is projected upward at time t = 0.00 s, from a point on a roof 70 m above the ground and experiences negligible air resistance. The ball rises, then falls and strikes the ground.
The initial velocity of the ball is Consider all quantities as positive in the upward direction. The velocity of the ball when it is above the ground is closest to
A) -38 m/s.
B) -30 m/s.
C) -23 m/s.
D) -15 m/s.
E) -45 m/s.
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