Question

A 40.0 kg box is placed on a 2.00 m tall shelf. If the box falls off the shelf, what is its kinetic energy as it strikes the ground?

Answer 1

m = 40 Kg , g=9.8 m/s² , h = 2 m

PE = m g h

PE = (40) (9.8) (2)

PE = 784 J

KE = PE

½m v² = m g h

½ v² = g h

½ v² = (9.8) (2)

½ v² = 19.6

v² = 19.6×2

v² = 39.2

V = √39.2

V = 6.26 m/s

KE = ½mv²

KE = ½(40) (6.26)²

KE =783.8 J