Question

A vehicle is driven along a straight horizontal track by a motor, which exerts a constant driving force. The vehicle starts from rest at t = 0 and the effects of friction and air resistance are negligible. If kinetic energy of vehicle at time t is E and power developed by the motor is P, which of the following graph is/ are correct?

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

Answer 2

Since force on the vehicle is constant, therefore, it will move with a constant acceleration. Let this acceleration be ‘a’ Then at time t, its velocity will be equal to v = a.t

Hence, at time t, the kinetic energy, E = = $\frac { 1 } { 2 } m a ^ { 2 } t ^ { 2 }$ The power associated with the force is equal P = F.v = F.at Hence, the graph between power & time will be straight line passing through the origin.

Hence, (1) is the correct choice.