Question

A ball of mass 200g falls from a height of 5m. what is its kinetic energy when it just reaches the ground? (g-9.8ms-2)

Answer 1

here potential energy must be equal to the kunetic enwrgy bcz the object is faaling from the height. so,
k.e=p.e=mgh
here, m=200g=0.2 kg
g=9.8m/s2
h=5m
so mgh=0.2*9.8*5=9.8joules

Answer 2

Given :-

• Mass of the ball (m) = 200 g
• Height (h) = 5 m
• Acceleration due to gravity (g) = 9.8 m/s²

To Find :-

• kinetic energy of the ball when it reaches the ground = ?

Solution :-

First convert the unit of the mass of ball from gram to kilogram :

• → Mass of ball = 200 g
• → Mass of ball = (200) ÷ (1000)
• → Mass of ball = 2 ÷ 10
• → Mass of ball = 0.2 kg

Hence,the mass of the ball is 0.2 kg.

According to the Question Now :-

Finding potential energy at higest point :

• → Potential energy = mass × Acceleration due to gravity × Height
• → Potential energy = 0.2 × 9.8 × 5
• → Potential energy = 1.96 × 5
• → Potential energy = 9.8 J

• Hence,the potential energy of the ball is 9.8 J.

As we know that, the Potential energy at the highest point is equal to the Kinetic energy at the lowest point.

Hence,from the above statement we can conclude that the Kinetic energy of the ball when it reaches the ground will be 9.8 J.

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