A 32.0 kg child descends a slide 4.00 m high. She reaches the bottom with a speed of 2.40 m/s, was the mechanical energy conserved? Explain your reasoning and identify the energy transformations involved.

Answer 1

ΔPE =m•g•Δh-0 = 32•9.8•4 =1254 J,
ΔKE =0 - m•v²/2 = - 32•(2.4)²/2 = -92.15J.
If the energy is conserved, ΔPE = - ΔKE.
They are not equal; therefore, the part of energy was lost, most likely, for friction.