What is the kinetic energy of an object with a mass of #1 kg# that has been in freefall for #4 s#?

1 Answer
Apr 6, 2018

Answer:

#approx 800J#

Explanation:

Given that it has been falling free for 4 seconds from rest we can use the equation:

#v=u+at#
#a=9.81 ms^-2#
#u=0#
#t=4 s#

Hence
#v=39.24 ms^-1#

Now using the kinetic energy equation:

#E_k=(1/2)mv^2#
#E_k=(0.5) times 1 times (39.24)^2#
#E_k=769.8 approx 800J# as we only had 1 significant figure in the question we should answer to 1 significant figure.