A spacecraft is initially traveling toward Mars. As the craft approaches the pla

ID: 2131250 • Letter: A

Question

A spacecraft is initially traveling toward Mars. As the craft approaches the

planet, rockets are fired and the spacecraft temporarily stops and

reorients itself. Then, at time t = 0 s, the rockets again fire causing the

craft to move toward Mars with a constant acceleration. At time t, the

crafts displacement is and its velocity . Assuming the acceleration

is constant, what would be its displacement and velocity at time 3t?

a) 3r

and 6v

b) 3r

and 3v

c) 6r

and 3v

d) 9r

and 3v

e) 9r

and 6v

Can someone explain why the answer is E?

v = at and d = 0 + at^2/2

v = 3a and d = 4.5a

d/v = 4.5/3 = 9 /6

that is answer E.

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