Question

Answer the following questions:

1. An object with mass M and velocity V has kinetic energy K= 1/2MV^2. If the velocity of the object is reduced to 1/5V, then its new kinetic energy is: a)1/5K b) 5K c)1/25K d) 25K

2. Velocity is a vector, therefore it has magnitude and direction. In a circular motion, the change in magnitude and direction of velocity respectively produce: a) centripetal acceleration and tangential acceleration b) tangential acceleration and centripetal acceleration c) tangential force and centripetal force d) centripetal force and tangential force

3. By the work and energy theorem, work is equal to the change in kinetic energy. If the unit of energy is Joule, then the unit (s) of work is (are): a) Kg x m/s^2 b) N/m c) N x m d) N

4.If two spheres of masses M subscript 1 and M subscript 2 move in opposite directions, one to the right and the other to the left. After the crash: a) the sphere of mass M subscript 1 remains at rest. b) the sphere of mass M subscript 2 remains at rest. c) the two spheres continue to move in one direction d) cannot be determined

5. A particle of mass M and velocity V has a kinetic energy K. If the energy of the particle changes to 25 K, then the velocity of the particle changes to: a) 25V b) 1/5V c) 5V d) 10V

Answer 1

1) When the velocity is V, the initial kinetic energy is

When the velocity is reduced to V/5, the new kinetic energy is.

Option (c) is the correct answer.

2) In circular motion the change in magnitude of the velocity produces tangential acceleration and change in direction of velocity produces centripetal acceleration.

Option (b) is the correct answer.

3) By work energy theorem, work done is change in kinetic energy. Given the unit of energy is Joule

Option (c) is the correct answer.

4) Here M1 and M2 are colliding from opposite directions. But since the initial velocities of M1 and M2 are not known, the after-effect of collision cannot be determined.

Option (d) is the correct answer.

5) When the particle has velocity V, the kinetic energy is K. Therefore,

When the kinetic energy of the particle changes to 25K, let the velocity be V'. Now,

Option (c) is the correct answer.