Kinetic Energy

Question 1

State the equation for kinetic energy

Answer 1

Ek = ½ × mv²
Kinetic energy = ½ mass × velocity²

Question 2

State the relationship between the changing stores in GPE and KE.

Answer 2

Assuming friction and drag is negligible:
Change in the store of GPE = Change in the store of KE

Question 3

A lady with a hat drops a ball from a cliff such that the ball falls a distance of 3m to the ground. The ball has a mass of 100g.
a. Determine the store of GPE above the ground of the ball.
b. Determine the speed at which the ball hits the ground.

Answer 3

a. E Ep = mgh
U 100g = 0.1kg
S Ep = 0.001 × 9.8 × 3
A ✔️
C 2.9J
b. Assuming drag is negligible (always state this!):
E Ek = ½ × m × v²
U ✔️
S Ek = 2.94J
2.94 = ½ × 0.1 × v²
A v = √2.94/ (½ ×0.1)
= √2.94/ 0.05
= 7.7m/s