A body of mass 2 kg kept at the top of a building of height 10 m possess a potential energy of 200 J. What will be the kinetic energy of this body when it hits the ground? (Neglect air resistance)
200 J
By the law of conservation of mechanical energy, when air resistance is neglected, the total mechanical energy (potential energy + kinetic energy) of a freely falling body stays constant during the fall.
At the top, the body is at rest, so its kinetic energy is zero and its total energy is all potential energy, 200 J. Just as it hits the ground, its height is zero, so its potential energy is zero and all of the energy has become kinetic energy.
Therefore, kinetic energy on hitting the ground = potential energy at the top = 200 J.
Check: with \(g = 10\) m/s2, the potential energy is \(mgh = 2 \times 10 \times 10 = 200\) J. The speed on reaching the ground is given by \(v^{2} = 2gh = 2 \times 10 \times 10 = 200\), so \(KE = \frac{1}{2}mv^{2} = \frac{1}{2} \times 2 \times 200 = 200\) J, the same value.
Hence, 200 J.
Similar Questions
A stretched rubber band possesses which form of energy due to its changed shape?
Which situation involves an increase in potential energy?
A cart of mass 20 kg starts from rest and accelerates uniformly along a straight horizontal track. If it reaches a speed of 6 m/s in 3 seconds, what is the work done on the cart during this time interval?
What will be the power delivered by a lamp that uses 120 joules of energy in 2 minutes?
When a ball rolls down a hill and comes to rest, how is the total energy of the ball-earth system maintained?
Which of the following quantities is needed to calculate the work done by a constant force?
Which scenario demonstrates a higher power output, assuming the same work is done in each?
Simple machines are best described as devices that _______________.
The kinetic energy of a body of mass 'X' kg is 200 J when it is moving with a velocity of 2 m/s. What will be the value of X?
When is the work done by a constant force on an object zero?
Important Questions from Work Power Energy
Which of the following is NOT correct regarding friction?
If a pump can raise 200 liters of water through a height of 300 meters in one minute, how much work can it do in one hour?
Which of the following is an example of kinetic energy?
How much kinetic energy does a 160 g cricket ball have when it is thrown at a speed of 22 m/s?
The movement of birds is an example of _______.
