What is the kinetic energy of an object with a mass of #9 kg# that has been in freefall for #3 s#?

1 Answer
David G.
Jan 17, 2016

First step is to find the velocity, which is #29.4 ms^1#, then use that to calculate the kinetic energy, #3889.6 J#.

Explanation:

The object starts at rest, so #u = 0ms^-1# at #t=0#. To find the velocity at #t=3# after accelerating at #a#, the acceleration due to gravity, #9.8ms^-2#:

#v=u+at = 0 + 9.8*3 = 29.4 ms^-1#

The kinetic energy is given by:

#E_k=1/2mv^2=1/2*9*29.4^2 = 3889.6J#

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