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__India Study Solution - Physics Guide__

### Work, Energy and Power

In continuation of Test Series Set 1 (Q. No. 1-10) and Test Series Set 2 (Q. No. 11-20), Test Series Set 4 (Q. No. 31-40) here you have carefully selected 10 MCQ practice questions with hints & solutions (given at the end) from the Physics chapter - Work, Energy and Power.

**Syllabus for IITJEE, NEET:**

Work done by a constant force and by a variable force, Unit of Work, Energy and Power, Work Energy, Theorem. Elastic and in-elastic collisions in one and two dimensions, Notions of Work and Energy, Law of Conservation of Energy, Potential and Kinetic Energies, Gravitational Potential Energy, and its conversion to Kinetic energy, Potential Energy of a spring. Conservative and Non-conservative Forces, Different forms of Energy, Three types of Equilibrium, Mass-Energy equivalence. Power.

*Solved MCQ Test Series – Set 3 (Q. No. 21-30)*
Question 21: A particle is projected at 60

^{O}to the horizontal with a kinetic energy K. The kinetic energy at the highest point is,
a. K b. Zero

c. K/4 d. K/2

Question 22: Two springs with spring constants k

_{1}and k_{2}(k1 ¹ k_{2}) are extended by the same force. If their elastic potential energies are U_{1}and U_{2}, then, U_{2}will be -
Question 23: A particle of mass 0.1kg is subjected to a force that varies with distance as shown in the adjacent diagram. If the particle starts its journey from rest at x = 0, its velocity at x = 12m will be -

a. 0 m/s b. 20√2 m/s

c. 20√3 m/s d. 40 m/s

Question 24: A ball released from a height 20m, hits the ground and rebounds to a height of 16m. The percentage loss of energy during collision is,

a. 20% b. 40% c. 25% d. 75%.

Question 25: A block of mass 50kg is projected horizontally on a rough horizontal floor. The coefficient of friction between the block and the floor is 0.1. The block strikes a light spring of stiffness k = 100N/m with a velocity 2m/s. The maximum compression of the spring is,

a. 1m b. 2m

c. 3m d. 4m

Question 26: A uniform meter scale of mass 2kg is suspended from one end. If it is displaced through an angle 60

^{O}from the vertical, the increase in its potential energy is,
a. 4.9J b. 9.8J c. 9.8√3J d. 4.9(2 – √3)J

Question 27: A rigid body of mass ‘m’ is moving in a circle of radius ‘r’ with a constant speed ‘v’. The force on the body is mv

^{2}/r and is directed towards the center. What will be the work done by this force in moving the body over half the circumference of the circle.
Question 28: A ball ‘A’ is released from rest when the block ‘B’ is on the ground (see adjacent fig.). For the block ‘B’ of mass ‘M’ to remain in contact with ground, the minimum mass of ‘A’ must be -

a. 2M b. M

c. M/2 d. None of these.

Question 29: A body of mass 1kg is thrown upwards with a velocity 20ms

^{–1}. It momentarily comes to rest after attaining a height of 18m. How much energy is lost due to air friction? (g = 10ms^{–2})
a. 20J b. 30J

c. 40J d. 10J

Question 30: A ball is released from certain height and rebounds after hitting the ground. If it loses 50% of its KE on striking the ground then it will attain a height again equal to -

^{}
a. one fourth of the initial height

b. three fourth of the initial height

c. half of the initial height

d. none of these.

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*Work, Energy and Power***More Practice**

**Questions, Test Series**

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