Advertisements
Advertisements
Question
A ball of mass 200 g falls from a height of 5 metres. What is its kinetic energy when it just reaches the ground? (g = 9.8 m/s2)
Solution
Mass of the ball, (m) = 0.2 kg
Height from which the ball is dropped, (h) = 5 m
Initial velocity of the ball, (u) = 0 m/s
Acceleration due to gravity, (g) = 9.8 m/s2
Let the final velocity of the ball when it just reaches the ground be (v)
We will use the third equation of motion to find the velocity of the ball when it just reaches the ground,
v2 = u2 + 2as
So,
v2 = 0 + 2(9.8)(5)
⇒ v2 = 98
Now we can find the kinetic energy as,
`K.E = 1/2 mv^2`
Therefore,
K.E = (1/2)(0.2)(98)
⇒ K.E = 9.8 J
So, the kinetic energy of the moving object is 9.8 J.
APPEARS IN
RELATED QUESTIONS
An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
The energy of a flying kite is kinetic energy.
Two toy-cars A and Bof masses 200 g and 500 g respectively are moving with the same speed. Which of the two has greater kinetic energy?
A ball of mass M is moving with a speed v. What is its kinetic energy?
A body of mass 10 kg is moving with a velocity 20 m s-1. If the mass of the body is doubled and its velocity is halved, find:
- the initial kinetic energy, and
- the final kinetic energy.
Two objects having equal masses are moving with uniform velocities of 2 m/s and 6 m/s respectively. Calculate the ratio of their kinetic energies.
A body of 2 kg falls from rest. What will be its kinetic energy during the fall at the end of 2 s? (Assume g = 10 m/s2)
What are the uses of mechanical energy?
When stored water falls down, potential energy of water is converted into ______.
The kinetic energy of a given body depends on the ______.
