Question

An object of mass 20 kg is raised to 5 m above the ground what is it's potential energy? If object is allowed to fall, find it's kineticenergy when it is half way down

Answer 1

P.E=mgh,
i.e. 20×5×10=1000, for g=10
Total energy=constant
at halfway P.E=20×2.5×10=500
P.E+K.E=1000
K.E=1000-500=500 AT HALF WAY

Answer 2

i) mass of object, m = 20 kg
height, h = 5m
acceleration due to gravity,g = 9.8 m/s^2
potential energy of object, PE= mgh
= 20×5×9.8 = 980J


(note: acceleration due to gravity can be taken as 9.8 or 10m/s^2)