A body of mass 2 kg moving with a velocity of ( i ^ + 2 j ^ - 3 k ^ ) ms - 1 collides with another body of mass 3 kg moving with a velocity of ( 2 i ^ + j ^ + k ^ ) ms - 1 . If they stick together, the velocity in ms - 1 of the composite body will be:

1 5 ( - 4 i ^ + 7 j ^ - 3 k ^ )

Physics - Work Energy Power - Quiz-6

The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm the potential energy stored in it is :

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4 U
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8 U
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16 U
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U/4

300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g = 10 m/s², work done against friction is :

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200 J
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100 J
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zero
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1000 J

When an object is shot from the bottom of a long, smooth inclined plane kept at an angle of 60 $°$ with horizontal, it can travel a distance $x_{1}$ along the plane. But when the inclination is decreased to 30 $°$ and the same object is shot with the same velocity, it can travel $x_{2}$ distance. Then $x_{1}$ : $x_{2}$ will be:

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$1 : 2 \sqrt{3}$
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$1 : \sqrt{2}$
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$\sqrt{2} : 1$
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$1 : \sqrt{3}$

A force F= 20+10y acts on a particle in the y-direction where F is in Newton and y in meter. Work done by this force to move the particle from y = 0 to y = 1m is:

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20 J
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30 J
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5 J
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25 J

A mass m is attached to a thin wire and whirled in a vertical circle. The wire is most likely to break when:

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inclined at an angle of $60^{0}$ from vertical.
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the mass is at the highest point.
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the wire is horizontal.
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the mass is at the lowest point.

A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s. How much work is needed to stop it?

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1 J
0%

3 J
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30 J
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2 J

A person applies a force $\vec{F}$ on a box inside a moving train. If $S_{1}$ is the displacement of box w.r.t. train and $S_{2}$ is the displacement of train w.r.t. ground, then the work done by the person in the frame of the earth will be

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$\vec{F} . {\vec{S}}_{1}$
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$\vec{F} . {\vec{S}}_{2}$
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$\vec{F} . ({\vec{S}}_{1} + {\vec{S}}_{2})$
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$\vec{F} . ({\vec{S}}_{1} - {\vec{S}}_{2})$

A body of mass 2 kg moving with a velocity of $(\hat{i} + 2 \hat{j} - 3 \hat{k})$ ms $^{- 1}$ collides with another body of mass 3 kg moving with a velocity of $(2 \hat{i} + \hat{j} + \hat{k})$ ms $^{- 1}$ . If they stick together, the velocity in ms $^{- 1}$ of the composite body will be:

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$\frac{1}{5} (8 \hat{i} + 7 \hat{j} - 3 \hat{k})$
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$\frac{1}{5} (- 4 \hat{i} + \hat{j} - 3 \hat{k})$
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$\frac{1}{5} (8 \hat{i} + \hat{j} - \hat{k})$
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$\frac{1}{5} (- 4 \hat{i} + 7 \hat{j} - 3 \hat{k})$

An object of mass 500 g initially at rest is acted upon by a variable force whose x-component varies with x in the manner shown. The velocities of the object at the points x = 8 m and x = 12 m would have the respective values of nearly:

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18 m/s and 24.4 m/s
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23 m/s and 24.4 m/s
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23 m/s and 20.5 m/s
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18 m/s and 20.5 m/s

A body of mass 5 kg is moving with a velocity of 10 m/s. Now a force that delivers a constant power of 75 watts is applied to it for 10 s in the same direction. The velocity of the body after 10 s will be

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$10 \sqrt{2} m / s$
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20 m/s
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40 m/s
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$25 \sqrt{2}$ m/s

A mass of 4kg falls from a height h on the pan. Initially, the spring is in its natural length and mass of spring and pan are negligible. Spring constant of the spring is 1000 N/m. The mass compresses the spring by 0.5 m. Then the height 'h' is

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2.00 m
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1.56 m
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4.0 m
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2.625 m

Human heartbeats 72 times per minute. It pumps 1 cc blood in each pulse under the pressure of $2 \times 10^{^{4}} N / m^{2} .$ The power of the heart is

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0.2 watt
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0.02 watt
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0.024 watt
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$2.2 \times 10^{- 1}$ watt

A body having an initial kinetic energy 2 J collides with an identical body at rest. The maximum loss of kinetic energy in the collision will be:

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2 J
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Zero
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1 J
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1.5 J

A particle is thrown at an acute angle with the horizontal. Select the incorrect statement.

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Power delivered by gravity is zero at all the point on the trajectory.
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Power delivered by gravity is zero only at one point.
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The average power of gravity is zero.
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During the one-half journey, the power is negative and during the other half, the power is positive.

What is the work done by friction when the body slides down the inclined surface from A to B?

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32 J
0%

16 J
0%

8 J
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Zero

Block A moves on the smooth surface and collides with the block B at rest. The maximum energy stored in the spring will be

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$\frac{1}{8} {mv}^{2}$
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$\frac{1}{4} {mv}^{2}$
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$\frac{1}{3} {mv}^{2}$
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$\frac{1}{2} {mv}^{2}$

An object of mass 2 kg falls from rest through a vertical distance 10 m and acquires a velocity of 10 m/s. The work done by the resistive force of air on the object is (g = 10 $m / s^{2}$ )

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200 J
0%

-200 J
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150 J
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-100J

A constant horizontal force is applied on a block kept at rest on a smooth horizontal surface. Its power (P) versus time (t) graph is best shown by

A block slides down an inclined plane of inclination 30° with a constant velocity. It then projected up with an initial speed of 6 m/s, the distance moved by it on the inclined before coming to rest is

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(1) 5 m
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(2) 1.8 m
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(3) 2.0 m
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(4) 2.4 m

The potential energy of a particle of mass 0.5 kg moving along x axis is given by

U = 2x (x - 3). The speed of the particle is maximum at

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x = 1 m
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x = 1.5 m
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X = 2 m
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x = 3 m
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4

Work energy theorem is valid in

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Only inertial frame of reference
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The only non-inertial frame of reference
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Both inertial and non-inertial frame of reference
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Does not depend on any frame of reference

A block of mass m is projected with speed v along the rough surface of an inclined plane of height h. If block comes to rest at the top of the surface, then work done by friction force is

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$- \frac{1}{2} {mv}^{2}$
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$m [gh - \frac{1}{2} v^{2}]$
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-mgh
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$m [gh + \frac{1}{2} v^{2}]$

A body of mass m moving with speed v collides head-on elastically with another identical body at rest. The percentage loss in kinetic energy of the first body will be:

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0%
0%

25%
0%

50%
0%

100%

If a body starts its motion along the smooth track from P as shown in the figure, then its velocity at the instant of leaving R is

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5 m/s
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15 m/s
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10 m/s
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20 m/s

The principle of conservation of energy and conservation of mechanical energy applicable respectively for

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Conservative and non-conservative forces
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Conservative and conservative force
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Non-conservative and conservative forces
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All forces and conservative forces

A particle of mass m is moving in a vertical circle of radius r. If the velocity of the particle at the uppermost point is $\sqrt{2 g r}$ , then its velocity at the lowermost point

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$\sqrt{7 gr}$
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$\sqrt{6 g r}$
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$\sqrt{5 g r}$
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2 $\sqrt{g r}$

A block having mass m is hanging by a string of length l. A variable horizontal force is applied on the block, which displaces the block slowly till the string makes an angle $θ$ with the vertical. Find the work done by the force.

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mgl
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mgl(1 - cos $θ$ )
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mglcos $θ$
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mgl(1 + cos $θ$ )

A particle is moving with kinetic energy E and momentum p. Which of the following graphs is possible between $\sqrt{E}$ and $\frac{1}{p}$ ?

Two vehicles are moving with the same kinetic energy. If the ratio of their masses is 1 : 3 then find the ratio of their stopping distances when both vehicles stop with the same retardation.

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1: 1
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3: 1
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9: 1
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1: 9

If the work done by the string on block A is W. Then work done by the string on the block B will be

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-W
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$- \frac{W}{2}$
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2W
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Zero

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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