JEE Main Physics: Work And Power Energy Quiz!

1. A small sphere of mass 'm' is released from rest from point A, and the sphere follows the path as shown in the figure. What should be the minimum height 'H', so that the sphere is able to complete the circle?

H = 3/2 R

H = 5/2 R

H = 27/2 R

H = 1/3 R

Explanation

2. A man of mass 60 kg takes 35 seconds to reach the top of a building using the stairs. How much time will be taken by another man of the same mass, if the powers developed by the first man and the second man are in the ratio of 4:7?

16 seconds

9 seconds

18 seconds

20 seconds

Explanation

3. The displacement of an object moving on a straight line varies according to the equation x = Ktⁿ, where t is time. If a constant power is supplied to the object then the value of 'n' will be:

1

3/2

1/3

2

Explanation

4. A particle of mass 'm' is moving in horizontal direction on a rough surface. The coefficient of friction varies as $bold italic mu bold space bold equals bold space bold K over bold x to the power of bold 3$ , where x is the distance from the origin and K is a positive constant. The particle starts moving from x = 1, in the direction away from the origin. What should be the minimum initial velocity, so that the particle never stops?

Explanation

5. Which of the following statement is correct?

Kinetic Energy of a system can be changed without changing its momentum

Work done on a system will always increase the potential energy of the system

Change in the total mechanical energy of the system is equal to the work done by a conservative force

None of these

a. Inelastic collisions are the examples in which the kinetic energy of the bodies changes but the momentum of the bodies remains conserved. b. Work done on a system will always increase the potential energy of the system: It will happen only in the case of conservative. In case of Non – Conservative forces, the work done may dissipate in form heat, sound etc. c. In case of conservative forces the work done is equal to the change in the potential energy.

Explanation

a. Inelastic collisions are the examples in which the kinetic energy of the bodies changes but the momentum of the bodies remains conserved. b. Work done on a system will always increase the potential energy of the system: It will happen only in the case of conservative. In case of Non – Conservative forces, the work done may dissipate in form heat, sound etc. c. In case of conservative forces the work done is equal to the change in the potential energy.

6. A particle of mass 'm' is moving with a variable velocity $bold italic v bold space bold equals bold space bold italic k square root of bold t bold comma$ where k is a positive constant. If the particle starts from rest, then calculate the work done by all the forces after the particle has travelled a distance 'x':

Explanation

7. Which of the following graph is the best representation of the kinetic energy of a projectile versus its horizontal displacement?

Explanation

8. A car of mass 'm' is driven with a constant power 'P'. What will be the speed of the car after traveling a distance's'?

Explanation

9. On a smooth semicircular track of radius 'R', a block of mass 'M' is given a velocity of $begin mathsize 12px style square root of 2 R g end root end style$ . The direction of velocity is parallel to the track at point C. The normal reaction between block and track at point 'B' is:

4Mg

2Mg

3Mg

5Mg

Explanation

10. An engine pumps water continuously through a nozzle. The water is coming out of the nozzle with a speed 'v'. At what rate the kinetic energy is imparted by the jet pump to the water jet. Mass per unit length of the water jet is 'm'.

Explanation