Physics - Work Energy Power - Quiz-7

If the pulley system with the ideal mechanical advantage of 4 requires a force of 15 N to lift a load of 45 N, then the efficiency of the pulley is

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25%
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30%
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40%
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75%

A small block of mass m is pulled by a light rope on a quarter circular track, having radius R. If the force applied on the rope is F always directed horizontally, then the work done by the force till the block reaches from A to B is:

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FR
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$FR \sqrt{2}$
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$F 2 πR$
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Zero

A stone of mass m is thrown from the earth's surface at an angle $α$ to the horizontal with an initial velocity $v_{0}$ . Ignoring the air drag, the power developed by gravitational force t second after the beginning of motion is:

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$mg (gt - v_{0} sinα)$
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${mgv}_{0} sinα \cdot t$
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$mg (g - vsinα \cdot t)$
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Zero

A car of mass 100 kg and traveling at 20 m/s collides with a truck weighing 1 tonne traveling at 9 km/h in the same direction. The car bounces back at a speed of 5 m/s. The speed of the truck after the impact will be:

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11.5 m/s
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5 m/s
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18 m/s
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12 m/s

If work done by the string on block A is W, shown in the given arrangement, then the work done by the string on block B is

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-W
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$- \frac{2 W}{3}$
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$\frac{3 W}{2}$
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$\frac{2 W}{3}$

Which of the following remains unchanged (for the system) during an inelastic collision?

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Mechanical energy
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Kinetic energy
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Momentum
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All of the above.

The position (in meter) of a particle of mass 1 kg confined to move along the y-axis varies with time (in second) as y= $t^{2}$ - 4t+ 5. The work done by all the forces acting on the particle during t = 0 to t = 4 s is

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8 J
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16 J
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32 J
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Zero

A particle is dropped from a height of 50 m. If the particle loses its 20% mechanical energy during the impact with the ground, up to what height will it rebound after the second impact?

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40 m
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36 m
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32 m
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28 m

A body of mass 2 kg is rotating in a vertical circle of radius 4 m. The difference in its kinetic energy at the top and bottom of the circle is:

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40 J
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80 J
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120
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160 J

If a stone is projected vertically upward from the ground with a speed of 10 m/s, then it's: (g = 10 $m / s^{2}$ )

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Potential energy will be maximum after 0.5 s
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Kinetic energy will be maximum again after 1 s
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Kinetic energy = potential energy at a height of 2.5 m from the ground
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Potential energy will be minimum after 1 s

A particle suspended by a light inextensible thread of length l is projected horizontally from its lowest position with velocity $\sqrt{4 g l}$ . The height from its lowest position at which particle will leave the circular path is:

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$\frac{3 l}{2}$
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$\frac{5 l}{3}$
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$\frac{4 l}{3}$
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2l

A mass M is suspended by a spring having a spring constant K. In equilibrium position mass M is given a speed u. Find further extension in the spring.

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$\sqrt{\frac{M}{K}} u$
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$\sqrt{\frac{2 M}{K}} u$
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$\sqrt{\frac{2 M}{K}} u + \frac{Mg}{K}$
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$\sqrt{\frac{M}{K}} u + \frac{Mg}{K}$

A block of mass 20 kg is being brought down by a chain. If block acquires a speed of 2 m/s in dropping down 2 m. Find work done by the chain during the process. (g = 10 $m / s^{2}$ )

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-360 J
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400 J
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360 J
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-280 J

A block of mass m is allowed to slide down a fixed smooth inclined plane of inclination $θ$ and slope length L. What is the power developed by the force of gravity, when the block reaches the bottom?

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$\sqrt{2 m^{2} L {(gsinθ)}^{3}}$
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$\frac{2}{3} {Lg}^{2} \sin θ$
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$\sqrt{\frac{2}{3} m^{2} {Lg}^{3}}$
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$mg \sqrt{2 gL \sin θ}$

A particle is projected at a time t = 0 with a speed $v_{0}$ and at an angle with the horizontal in a uniform gravitational field. Then which of the following graph represents power delivered by gravitational force against time (t)?

Which of the following is not correct?

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Viscous force is a non-conservative force.
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Force of friction is non-conservative.
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If R is the horizontal range of an oblique the projectile, then the kinetic energy of the projectile is minimum after covering a horizontal the distance of R/2 considering air resistance.
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Work done in stretching a spring successively by length x from natural length are in the ratio 1:3.

The potential energy U of a system is given by $U = A - {Bx}^{2}$ (where x is the position of its particle and A, B are constants). The magnitude of the force acting on the particle is:

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Constant
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Proportional to x
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Proportional to $x^{2}$
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Proportional to $(\frac{1}{x})$

A person-1 stands on an elevator moving with an initial velocity of 'v' & upward acceleration 'a'. Another person-2 of the same mass m as person-1 is standing on the same elevator. The work done by the lift on the person-1 as observed by person-2 in time 't' is:

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$m (g + a) (vt + \frac{1}{2} {at}^{2})$
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$- mg (vt + \frac{1}{2} {at}^{2})$
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0
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$ma (vt + \frac{1}{2} {at}^{2})$

If a body of mass 2 kg is moved in the conservative field from point A to B in three different paths, then work done will be

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$W_{I} < W_{II} < W_{III}$
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$W_{I} > W_{II} > W_{III}$
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$W_{I} = W_{II} = W_{III}$
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$W_{I} > W_{II} = W_{III}$

Two pendulum bobs A and B of mass m and 2m respectively are simultaneously released from a height H above the lowest point, making an elastic collision at the lowest point. If after the first collision A and B rise to heights $h_{1} and h_{2}$ respectively, then $h_{1} + 2 h_{2}$ is:

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3H
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H
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$\frac{H}{3}$
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$\frac{2 H}{3}$

A particle is moving along the x-axis under a conservative force and its potential energy U varies with x co-ordinate as shown in the figure. Then force is positive at:

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A
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C, D
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B
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D, E

A block of mass 'm' is connected to a spring of force constant K. Initially, the block is at rest and the spring is relaxed. A constant force F is applied horizontally towards the right. The maximum speed of the block will be:

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$\frac{F}{\sqrt{2 mK}}$
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$\frac{\sqrt{2} F}{\sqrt{mK}}$
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$\frac{F}{\sqrt{mK}}$
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$\frac{2 F}{\sqrt{2 mK}}$

Two blocks A and B of mass m and 4m at rest are displaced through identical paths due to identical net forces, then

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Their speeds are in the ratio, $\frac{v_{A}}{v_{B}} = \frac{1}{1}$
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Work done on the blocks is in the ratio, $\frac{W_{A}}{W_{B}} = \frac{1}{1}$
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Their kinetic energies are in the ratio, $\frac{K_{A}}{K_{B}} = \frac{1}{4}$
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All of these

For the path wxyz in a conservative field, the amount of work done in carrying a body from w to x and from x to y and from y to z are 2 J. 4 J and 6 J respectively. The work done in carrying the body from w to z will be

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12 J
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2 J
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4 J
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6

20 J of work is done to increase the length of a light spring by 1 cm from its natural length. Work done in increasing its length further by 1 cm is:

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60 J
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40 J
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30 J
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20 J

The work-energy theorem is the scalar form of Newton's

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The first law of motion
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The second law of motion
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Third law of motion
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All of these

A pendulum bob is made to move along a vertical circle such that it passes the highest point with critical speed. The ratio of centripetal and tangential acceleration when the string becomes horizontal is

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

A block of mass m is given a speed v when the spring of constant k is in its natural length as shown in the figure. The remaining kinetic energy of the block when spring is compressed by half of the maximum compression is:

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25%
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50%
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75%
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Any value of less than 50%

A body of mass m moving at a certain speed suffers a perfectly inelastic collision with a body of mass M at rest. The ratio of the final kinetic energy of the system to the initial kinetic energy will be:

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$\frac{m}{m + M}$
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$\frac{M}{m + M}$
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$\frac{m + M}{m}$
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$\frac{m + M}{M}$

A constant force is applied on a body of mass 2 kg to give it a displacement $s = \frac{1}{2} t^{2}$ . Work done by agent applying the force up to time t = 3 s is

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3 J
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9 J
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18 J
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2 J

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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