A laser is thrown upward with a speed of #12# #ms^-1# on the surface of Planet X where the acceleration due to gravity is #1.5# #ms^-2# and there is no atmosphere. How long does it take for the laser to reach the maximum height?

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Answer 1 · 2017-06-17T12:34:28

#t = (v-u)/a=(0-12)/-1.5=8# #s#

We can use #v=u+at#.

The final velocity at the top of of the trajectory is #v=0#.

The initial velocity is #u=12# #ms^-1# and the acceleration is #-1.5# #ms^-1# (since we chose upward as positive).

Rearranging:

#t = (v-u)/a=(0-12)/-1.5=8# #s#