Question

* A 5 kg ball is dropped from a height of 20 m. How much kinetic energy will it have 10 m above the ground? a. 490 J b. 392 J C. 480 J d. 100 J​

Answer 1

A. 490

Step-by-step explanation:

soln

mass = m = 5kg

Height = h = 10m

Acceleration due to gravity = g = 9.8ms²

K.E = 1/2 × mass × (velocity)²

Recall from equations of motion

v² = u² + 2gh

Therefore,

K.E = 1/2 × mass × ( u² + 2gh)

K.E = 1/2 × 5 × ( 0² + 2×10×9.8)

K.E = 1/2 × 5 × 196

K.E = 1/2 × 980

K.E = 490 Joules