The energy of the baby is gravitational potential energy, and it is equal to the weight of the baby times its height from the ground:
[tex]U=(mg) h[/tex]
where
mg=20 N is the weight (the mass times the gravitational acceleration)
h=1.5 m is the height from the ground
If we plug the numbers into the equation, we find
[tex]U=(mg)h=(20 N)(1.5 m)=30 J[/tex]
