HARD

JEE Main/Advance

IMPORTANT

Earn 100

A carpet of mass $M$ made of inextensible material is rolled along its length in the form of a cylinder of radius $R$ and is kept on a rough floor. The carpet starts unrolling without sliding on the floor when a negligibly small push is given to it. Calculate the horizontal velocity of the axis of the cylindrical part of the carpet when its radius reduces to $R / 2$ .

Important Questions on Work, Energy and Power

HARD

JEE Main/Advance

IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 1

A small solid ball of density half that of water falls freely under gravity from a height of

19.6 m

and then enters into water. Up to what depth will the ball go? How much time will it take to come again to the water surface? Neglect air resistance, viscosity effects of water and energy loss due to collision at the water surface.

(g = 9.8 m s^{- 2})

EASY

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IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 2

If the potential energy of a spring is

V

on stretching it by

2 cm

, then its potential energy when it is stretched by

10 cm

will be

EASY

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IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 3

In a circus, stuntman rides a motorbike in a circular track of radius

R

in the vertical plane. The minimum speed at highest point of track will be,

HARD

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IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 4

A particle is moving in a vertical circle. The tensions in the string when passing through two positions at angles

30 °

and

60 °

from downward vertical are

T_{1}

and

T_{2}

respectively. Then

MEDIUM

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IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 5

Sand drops from a stationary hopper at the rate of

5 kg s^{- 1}

falling on a conveyor belt moving with a constant speed of

2 m s^{- 1} .

What is the force required to keep the belt moving, and what is the power delivered by the motor moving the belt?

MEDIUM

JEE Main/Advance

IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 6

A particle of mass

4 m

which is at rest explodes into three fragments. Two of the fragments, each of mass

m

are found to move with a speed

v

each in mutually perpendicular directions. The minimum energy released in the process of explosion is:

HARD

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IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 7

The force of attraction between the positively charged nucleus and the electron in a hydrogen atom is given by

f = k \frac{e^{2}}{r^{2}}

Assume that the nucleus is fixed. The electron, initially moving in an orbit of radius

R_{1}

jumps into an orbit of smaller radius

R_{2} .

The decrease in the total energy of the atom is.

EASY

JEE Main/Advance

IMPORTANT

Alpha Question Bank for Engineering: Physics>Chapter 8 - Work, Energy and Power>Exercise - 1>Q 8

A block of mass $m$ is pulled on a rough horizontal surface which has a friction coefficient $μ$ . A horizontal force $F$ is applied which is capable of moving the body uniformly with speed $v$ . Find the work done on the block in time $t$ by

(a) weight of the block,

(b) Normal reaction by surface on the block,

(d) force $F$ ,

Important Questions on Work, Energy and Power

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