Question

17A boy throws a ball of mass 200 g with a velocity 20m * s ^ - 1 at an angle of 40 degrees with the horizontal. What is the kinetic energy of the ball at the highest point of the

Answer 1

At highest position, occurs only horizontal component of velocity
e.g., V = ucosθ, here θ is the angle of inclination of initial velocity with horizontal
So, V = 20 cos40°
Know, kinetic energy = 1/2 mV²
= 1/2 × (200/1000) kg × {20cos40°}² J
= 1/2 × 0.2 × 400cos²40° J
= 0.1 × 400 × 0.586 [ ∵ cos²40° = 0.586 ]
= 40 × 0.586 J
= 23.54 J