Question

A 20kg ball is thrown upward with speed of 4m s -1. a) Find its potential energy when it reaches the highest point b) Calculate the maximum height it reaches​

Answer 1

Answer:

(a) 160 J

(b) 0.8 m

Explanation:

Given :

mass of the ball, m = 20 kg

initial speed, u = 4 m/s

To find :

(a) the potential energy of the ball when it reaches the highest point

(b) the maximum height it reaches

Solution :

First, let's find the maximum height the ball reaches using suitable equation of motion.

At maximum height, the speed of the object becomes 0 m/s

So, final speed, v = 0 m/s

We know, acceleration due to gravity, g = 10 m/s²

Since it's an upward motion i.e., against the gravity ;

a = -g = -10 m/s²

Using v² - u² = 2as equation :

⇒ 0² - 4² = 2 × (-10) × s

⇒ -16 = -20s

⇒ 16 = 20s

⇒ s = 16/20

⇒ s = 0.8 m

∴ The maximum height the ball reaches is 0.8 m

The potential energy of an object is the energy possessed by it by virtue of its position.

$\longmapsto \bf P.E = mgh$

Substituting the values, we get

P.E = 20 × 10 × 0.8

P.E = 160 J

∴ The potential energy of the ball when it reaches maximum point is 160 J