Question

Kinetic energy of a body depends on
A) Mass
B) Speed
C) Frame of reference
D) All of the above

Answer 1

Hint: Kinetic energy is the energy possessed by a body in motion. So a body in motion will have a velocity and a mass. Also, the velocity of a body can vary depending on the frame of reference.

Complete step by step answer:
We are all familiar with the equation of the kinetic energy of a body of mass m moving with a velocity v, it is given by,
$\text{Kinetic Energy (K}\text{.E)}=\dfrac{1}{2}m{{v}^{2}}$
From the above equation, it is clear that the kinetic energy of a body depends on its mass m and also on the square of its velocity v.
The velocity of a body is different in different frames of reference. Suppose a person B is sitting in a bus and sees a person A sitting in front of him. According to B, A is at rest. But for a person C, who is looking at person A from the ground, will see A moving with a velocity which is equal to the velocity of the bus. So the B and C perceive the velocity of the person A differently.
So the kinetic energy associated with A according to B and C will also be different. So we can say that the kinetic energy of a body is dependent upon the frame of reference.
So the kinetic energy of a body depends on its mass, velocity and frame of reference.
So the answer to the question is option (D)- All of the above.

Note: The work done in increasing the velocity of a body of mass $\text{m}$ from ${{\text{v}}_{\text{1}}}$ to ${{\text{v}}_{\text{2}}}$ is given by the change in kinetic energy associated with the body. (This is only applicable when a conservative force acts on the body.)
$\text{Work Done (W)}=\dfrac{1}{2}m{{v}_{1}}^{2}-\dfrac{1}{2}m{{v}_{2}}^{2}$
The total energy of a body which is the sum of the potential and kinetic energy is independent of the frame of reference.