Question

If the kinetic energy of the body of fixed mass is constant then which of the following statement is correct:

a) Its velocity must be constant

b) Its speed must be constant

c) Its acceleration must be zero

1. Only a is correct
2. Only b is correct
3. Only c is correct
4. All are correct

Answer 1

Correct Answer - Option 2 : Only b is correct

CONCEPT:

Kinetic energy

• The energy possessed by a body due to the virtue of its motion is called kinetic energy.

\(\Rightarrow KE=\frac{1}{2}mv^{2}\)

Where KE = kinetic energy, m = mass and v = speed

EXPLANATION:

• The kinetic energy of the body of mass m and the speed v is given as,

\(\Rightarrow KE=\frac{1}{2}mv^{2}\)

• So, if mass is constant, we can say the kinetic energy can only be constant, if speed is constant.
• If the direction of the body changes its direction without changing the speed, its velocity will change because velocity is a vector quantity, and since the velocity changes so the acceleration will not be zero.
• Velocity is changing but speed is not changing in case of direction change. Hence, kinetic energy is not changing. 

Hence option only b is correct considering the above factors.