A constant torque acting on a uniform circular wheel changes its angular momentum from L to 4 L in 4 seconds.The magnitude of torque is :

A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 m s^-1 to 3.5 m s^-1 in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force ?

Prove that the time rate of change of the angular momentum of a particle is equal to the torque acting on it.

If no external torque acts on a body. will its angular velocity remain conserved?

A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90km/h. its velocity is slowed down to 18 km/h in 4 seconds by an unbalanced external force. Calculate the acceleration and change in momentum . Also calculate the magnitude of the force required.

A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90km/h. its velocity is slowed down to 18 km/h in 4 seconds by an unbalanced external force. Calculate the acceleration and change in momentum . Also calculate the magnitude of the force required.

A closely wound solenoid of 800 turns and area of cross section 2.5×10^-4 m^2 carries a current of 3.0 A. If the solenoid is free to turn about the vertical direction and a uniform horizontal magnetic field of 0.25 T is applied, what is the magnitude of torque on the solenoid when its axis makes an angle of 30^@ with the direction of applied field?

A particle of mass m is moving in yz-plane with a uniform velocit v with its trajectory running paralel to + ve y-axis and intersecting z-axis at z = a show in the figure. The change in its angular momentum about the origin as it bounces elastically from a wal at y = constant is