What is the kinetic energy of an object with a mass of #3 kg# that has been in freefall for #2 s#?

1 Answer
May 26, 2018

Answer:

E_k =600 J

Explanation:

from the first movument law
#s= s° + v°t + 1/2 a t^2#
but s°=0 and v° = 0 so
#s= 1/2 a t^2= 1/2 10 m/s^2 (2s)^2 = 20 m#
the kinetic energy is like the potential energy lost
#E_w= mgh = 3kg xx 10 m/s^2 xx 20m = 600 J#
#E_k= 600 J#
otherwise you can have also
#v= at= 10 m/s^2 xx 2 s = 20 m/s#
#E_k =1/2 m xx v^2 = 1/2 xx 3 kg xx (20m/s)^2=600J#