Question

A 3-kg ball is thrown with a speed of 8 m/s at an unknown angle above the horizontal. The ball attains a maximum height of 2.8 m before striking the ground.
If air resistance is negligible, what is the value of the kinetic energy of the ball at its highest point?

Answer 1

Answer:

13.5 J

Explanation:

mass of ball, m = 3 kg

maximum height, h = 2.8 m

initial speed, u = 8 m/ s

Angle of projection, θ

use the formula of maximum height

$H = \frac{u^{2}Sin^{2}\theta }{2g}$

$2.8 = \frac{8^{2}Sin^{2}\theta }{2\times 9.8}$

Sin θ = 0.926

θ = 67.8°

The velocity at maximum height is u Cosθ = 8 Cos 67.8 = 3 m/s

So, kinetic energy at maximum height

$K=\frac{1}{2}mv^{2}$

K = 0.5 x 3 x 3 x 3

K = 13.5 J