Question

a 45 kg girl is bouncing on a trampoline. during a certain interval after she leaves t he surface of the trampoline, her kinetic energy decreases to 220 J from 420 J. how high does she rise during this interval neglect air resistance

Answer 1

Answer: Height = 0.45m

Explanation:

According to the conservation of energy, When there are no interactions outside a system ie  neglecting air resistance,The change in kinetic energy is equal to the change in potential energy in a closed system.

Therefore the kinetic energy decrease, the potential energy increases, and  decreases for increase in Kinetic energy

an is represented by the formulae

ΔKinetic energy + ΔPotential energy = 0

ΔKinetic energy = -ΔPotential energy ( where negative sign represent decrease as kinetic energy increases.

ΔK.E=ΔP.E

420J- 220J= mgh

mass = 45kg

g =gravitational acceleration =9.8 m/s^2

200J = 45 X 9.8 X h

h = 200/45 x 9.8 /= 0.45m