# Physics

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Just before landing on mars, a spaceshuttle turns on its retroengine and eventually comes to a complete stop 15 meters above the planets surface. It then drops freely down to the surface. How long does it take to fall to the surface.What is the impact speed?

Is the answer 1.5 seconds for the first oneand its impact speed 9.8?

• Physics -

Gravitational acceleration on Mars is 37.7% of gravity on earth
g mars = 9.8 * .377 = 3.7 m/s^2
v = a t
d = .5 a t^2

15 = .5 (3.7) t^2
t^2 = 8.1
t = 2.85 s
v = 3.7*2.85 = 10.5 m/s

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