CBSE Questions for Class 11 Medical Physics Work, Energy And Power Quiz 12 - MCQExams.com

A sphere $$A$$ moving with speed $$u$$ and rotating with an angular velocity $$\omega$$ makes a head-on elastic collision with an identical stationary sphere $$B$$. There is no friction between the surfaces of $$A$$ and $$B$$. Choose the correct alternative(s). Discard gravity.
  • $$A$$ will stop moving but continue to rotate with an angular velocity $$\omega$$
  • $$A$$ will come to rest and stop rotating
  • $$B$$ will move with speed $$u$$ without rotating
  • $$B$$ will move with speed $$u$$ and rotate with an angular velocity $$\omega$$.
Find the horizontal component of the resultant force, which the axis will exert on the plate after the impact.
  • $$\displaystyle F=\frac{8Mv^2}{\displaystyle l{\left(1+\frac{4M}{3m}\right)}^2}$$
  • $$\displaystyle F=\frac{4Mv^2}{\displaystyle l{\left(1+\frac{4M}{3m}\right)}^2}$$
  • $$\displaystyle F=\frac{4Mv^2}{\displaystyle l{\left(1-\frac{4M}{3m}\right)}^2}$$
  • $$\displaystyle F=\frac{8Mv^2}{\displaystyle l{\left(1-\frac{4M}{3m}\right)}^2}$$
The work done by the tension T in the above process is

188679.jpg
  • $$Zero$$
  • $$T(L-L\cos \theta )$$
  • $$-TL$$
  • $$-TL\,\sin \theta $$
A force $$F=-6{x}^{3}$$ is acting on a block moving along x-axis. Work done by this force is:
  • Positive in displacing the block from $$x=3$$ to $$x=1$$.
  • Positive in displacing the block from $$x=-3$$ to $$x=-1$$.
  • Negative in displacing the block from $$x=0$$ to $$x=4$$.
  • Zero in displacing the block from $$x=-2$$ to $$x=+2$$.
Find the angular velocity of the rod after the collision.
  • $$\displaystyle\omega=\frac{3v}{(4+\eta)l}$$
  • $$\displaystyle\omega=\frac{12v}{(4+\eta)l}$$
  • $$\displaystyle\omega=\frac{3v}{(4-\eta)l}$$
  • $$\displaystyle\omega=\frac{12v}{(4-\eta)l}$$
Calculate the work done on the tool by $$\vec{F}$$ if this displacement is along the straight line $$y =x$$ that connects these two points.
  • $$2.50 J$$
  • $$500 J$$
  • $$50.6 J$$
  • $$2 J$$
A particle slides along a track with elevated ends and a flat central part as shown in the Figure below. The flat portion BC has a length $$l=3.0 m$$. The curved portions of the track are frictionless. For the flat part the coefficient of kinetic friction is $$\displaystyle \mu _{k}= 0.20,$$ the particle is released at point A which is at height $$h=1.5 m$$ above the flat part of the track. Where does the particle finally comes to rest?


240697_a738f9087cc3456b9488664034340fc7.bmp
  • The particle comes to rest at the center. of the flat part.
  • The particle comes to rest at $$\frac{1}{4}$$th distance from the point B of the flat part.
  • The particle comes to rest at $$\frac{3}{4}$$th distance from the point B of the flat part.
  • The particle comes to rest at point B
The value of ratio $$M/m$$ is
218592_228d4be5db7d4985b39de62c52f2c80a.png
  • $$2:3$$
  • $$3:2$$
  • $$4:3$$
  • $$3:4$$
A force $$\displaystyle F= -\frac{k}{x^{2}}\left ( x\neq 0 \right )$$ acts on a particle in x-direction. Find the work done by this force in displacing the particle from. $$\displaystyle x= +a\:$$to$$\:x= +2a.$$ Here, $$k$$ is a positive constant.
  • $$\displaystyle  -\frac{k}{2a}$$
  • $$\displaystyle  \frac{k}{2a}$$
  • $$\displaystyle  -\frac{k}{a}$$
  • $$\displaystyle  +\frac{k}{a}$$
An object is displaced from position vector $$\displaystyle \vec{r}_{1}= \left ( 2\hat{i}+3\hat{j} \right )m\:$$ to$$ \:\vec{r}_{2}= \left ( 4\hat{i}+6\hat{j} \right )$$ m under a force $$\displaystyle \vec{F}= \left ( 3x^{2}\hat{i}+2y\hat{j} \right )N.$$ Find the work done by this force.
  • $$83 J$$
  • $$41.5 J$$
  • $$166 J$$
  • $$164 J$$
Which of the following statements is correct regarding the work done $$\vec{F}$$ along these two paths.
  • Work done on x-axis is zero
  • Work done on x-axis is less than on y-axis
  • Work done on x-axis is more than on y-axis but not zero
  • Data insufficient
Energy stored in the bonds of molecules is a form of:
  • heat energy
  • potential energy'
  • chemical energy
  • light energy
The work done by the varying force in changing the angular displacement from 0 to $$\theta $$ is

188679.jpg
  • $$Wh$$
  • $$FL\,\sin \theta$$
  • $$Fh$$
  • $$\dfrac{1}{2}FL\,\sin \theta $$
A cutting tool under microprocessor control has several forces acting on it. One force is $$\vec{F}=-\alpha xy^2\hat{j}$$, a force in the negative y-direction whose magnitude depend on the position of the tool. The constant is $$\alpha  = 2.50\ N/m^3$$. Consider the displacement of the tool from the origin to the point  $$x = 3.00 \,m, y = 3.00 \,m$$. Calculate the work done on the tool by $$\vec{F}$$ if the tool is first moved out along the x-axis to the point $$x = 3.00m, \:y= 0m $$ and then moved parallel to the y-axis to $$x = 3.00m, y = 3.00 \,m$$.
  • $$67.5 J$$
  • $$85 J$$
  • $$102 J$$
  • $$7.5 J$$
A uniform rod of mass $$m$$ and length $$l$$ is pivoted at point $$O$$. The rod is  initially in vertical position and touching a block of mass $$M$$ which is a rest on a horizontal surface. The rod is given a slight jerk and it starts rotating about point $$O$$ This causes the block to move forward as shown. The rod loses contact with the block at $$\theta =30^{\circ}$$ All surfaces are smooth. Now answer the following questions. The velocity of block when the rod loses contact with the block is
218600_eeb91b7521c841de97c388b6d5caf9cf.png
  • $$\displaystyle \frac{3gl}{4}$$
  • $$\displaystyle \frac{5gl}{4}$$
  • $$\displaystyle \frac{6gl}{4}$$
  • $$\displaystyle \frac{7gl}{4}$$
A shown in figure there is a spring block system. Block of mass $$500$$ g is pressed against a horizontal spring fixed at one end to compress the spring through $$5.0$$ cm. The spring constant is $$500$$ N/m. When released, the block moves horizontally till it leaves the spring. Calculate the distance where it will hit the ground $$4$$ m below the spring?
302903_f059fc6c3b97455b82b0b69a3ab9f2d3.png
  • $$6 m$$
  • $$4 m$$
  • $$8 m$$
  • $$\sqrt { 2 }$$m
A ball of mass '$$m$$' moves perpendicularly to a wall with a speed $$v$$, strikes it and rebounds with the same speed in the opposite direction. What is the direction and magnitude of the average force acting on the ball due to the wall?
  • $$2 m{v}/{t}$$ away from the wall
  • $$3 m{v}/{t}$$ away from the wall
  • $$1 m{v}/{t}$$ away from the wall
  • $$4 m{v}/{t}$$ away from the wall
An athlete in the Olympic games covers a distance of $$100$$m in $$10$$s. His kinetic energy can be estimated to be in the range. (Assume weight = 60kg)
  • $$200J-500J$$
  • $$2\times 10^5J-3\times 10^5J$$
  • $$20000J-50000J$$
  • $$2000J-5000J$$
From $$x=0$$ to $$x=6$$, the force experienced by an object varies according to the function $$F\left(x\right)=\sqrt{6x-{x}^{2}}$$, as shown above. What is the work done by this force as the object moves from $$x=0$$ to $$x=3$$?
Assume all numbers are given in standard units.
495640.jpg
  • $$0 J$$
  • $$4.5 J$$
  • $$7.1 J$$
  • $$9.0 J$$
  • $$14.0 J$$
A moving coin hits another coin and sets it into motion. In this case, energy from the moving coin is _________ to the other coin.
  • Flown
  • Taken
  • Not transferred
  • Transferred
A helicopter flying in the air has :
  • Only kinetic energy but not potential energy
  • Only potential energy but not kinetic energy
  • Both potential and kinetic energy
  • Neither kinetic nor potential energy
A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes up to 2 in height further, find the magnitude of the force. Consider g = $$10 m/s^2$$
  • 16 N
  • 20 N
  • 22 N
  • 180 N
A spherical ball A of mass $$4\ kg$$, moving along a straight line strikes another spherical ball B of mass $$1\ kg$$ at rest. After the collision, A and B move with velocities $$v_{1}\ ms^{-1}$$ and $$v_{2}\ ms^{-1}$$ respectively making angles of $$30^{\circ}$$ and $$60^{\circ}$$ with respect to the original direction of motion of ball A. The ratio $$\dfrac {v_{1}}{v_{2}}$$ will be:
  • $$\dfrac {\sqrt {3}}{4}$$
  • $$\dfrac {4}{\sqrt {3}}$$
  • $$\dfrac {1}{\sqrt {3}}$$
  • $$\sqrt {3}$$
Under the action of a force, $$2kg$$ body moves such that its position $$x$$ as a function of time is given by $$x={t}^{3}/3$$ where $$x$$ is in meters and $$t$$ in seconds. The work done by the force in the first two seconds is:
  • $$1.6J$$
  • $$16J$$
  • $$160J$$
  • $$1600J$$
A car of mass $$m$$ starts moving so that its velocity varies according to the law $$v=\beta \sqrt { s }$$, where $$\beta$$ is a constant, and $$s$$ is the distance covered. The total work performed by all the forces which are acting on the car during the first $$t$$ seconds after the beginning of motion is:
  • $${ m\beta }^{ 4 }{ t }^{ 2 }/8$$
  • $${ m\beta }^{ 2 }{ t }^{ 4 }/8$$
  • $${ m\beta }^{ 4 }{ t }^{ 2 }/4$$
  • $${ m\beta }^{ 2 }{ t }^{ 4 }/4$$
Work done in time $$t$$ on a body of mass $$m$$ which is accelerated from rest to a speed $$v$$ in time as a function of time $$t$$ is given by
  • $$\cfrac { 1 }{ 2 } m\cfrac { v }{ { t }_{ 1 } } { t }^{ 2 }\quad $$
  • $$m\cfrac { v }{ { t }_{ 1 } } { t }^{ 2 }$$
  • $$\cfrac { 1 }{ 2 } m{ \left( \cfrac { v }{ { t }_{ 1 } } \right) }^{ 2 }{ t }^{ 2 }$$
  • $$\cfrac { 1 }{ 2 } m\cfrac { v }{ { t }_{ 1 }^{ 2 } } { t }^{ 2 }$$
Which of the following potential energy curves possibly describe the elastic of two billiard balls?
Here $$r$$ is the distance between centres of the balls.
Two small particles of equal masses start moving in opposite directions from a point $$A$$ in a horizontal circular orbit. Their tangential velocities are $$v$$ and $$2v$$ respectively, as shown in the figure. Between collisions, the particles move with constant speeds. After making how many elastic collisions, other than that at $$A$$, these two particles will again reach the point $$A$$?
766003_8244fe1a98344c93ab16a45c4d89dfe9.png
  • $$4$$
  • $$3$$
  • $$2$$
  • $$1$$
By applying a force $$\vec{F} = (3xy - 5z)\hat{j} + 4z\hat{k}$$ a particle is moved along the path $$y=x^{2}$$ from point $$(0,0,0)$$ to point $$(2,4,0)$$.  The work done by the $$F$$ on the particle is 
984153_d5bfb1303934402cb95cb0b3de23118b.png
  • $$\dfrac{280}{5}$$
  • $$\dfrac{140}{5}$$
  • $$\dfrac{232}{5}$$
  • $$\dfrac{192}{5}$$
The bob $$A$$ of a pendulum of mass $$m$$ released from horizontal to the vertical hits another bob $$B$$ of the same mass at rest on a table as shown in figure. If the length of the pendulum is $$1\ m$$, what is the speed with which bob $$B$$ starts moving. (Neglect the size of the bobs and assume the collision to be elastic) (Take $$g = 10\ ms^{-2})$$.
941420_35fdcc082e1e49f3b260b592e3b33582.png
  • $$4.47\ ms^{-1}$$
  • $$5.47\ ms^{-1}$$
  • $$6.47\ ms^{-1}$$
  • $$3.47\ ms^{-1}$$
Speed of $$C$$ just after collison is
981767_a41cc318e3624723b0202f02772a1cde.PNG
  • $$2 m/s$$
  • $$2 \sqrt{2} m/s$$
  • $$5 m/s$$
  • $$(\sqrt{2} - 1) m/s$$
A man is standing on a plank which is placed on a smooth horizontal surface. There is sufficient friction between the feet of man and plank. Now man starts running over plank, correct statement is/are
987582_c6f52bbab2284e67bf28c46120f025a6.PNG
  • Work done by friction on the man with respect to the ground is negative.
  • Work done by friction on the man with respect to the ground is positive.
  • Work done by friction on the plank with respect to the ground is positive.
  • Work done by friction on the man with respect to the plank is zero.
Two bodies $$A$$ and $$B$$ have masses $$20\ kg$$ and $$5\ kg$$ respectively. If they acquire the same kinetic energy. Find the ratio of thier velocities.
  • $$\dfrac {1}{2}$$
  • $$2$$
  • $$\dfrac {2}{5}$$
  • $$\dfrac {5}{6}$$
A body is acted upon by a force which is proportional to the distance covered. If distance covered is represented by s, then work done by the force will be proportional to.
  • s
  • $$s^2$$
  • $$\sqrt{s}$$
  • None of the above
A particle of mass $$m$$ is moving horizontally with a constant velocity $$v$$ towards a rigid wall that is moving in opposite direction with a constant speed $$u$$. Assuming elastic impact between the particle and wall the work done by the wall in reflecting the particle is equal to:
  • $$\left( \dfrac{1}{2} \right) m{ \left( u+v \right) }^{ 2 }\quad \quad $$
  • $$\left( \dfrac{1}{2} \right)4 mv\left( { u }+{ v } \right) $$
  • $$\dfrac{1}{2}muv$$
  • None of these
 A particle is taken from A to point B under the influence of a force field. Now it is taken from B to A and it is observed that the work done in taking the particle from A to B is not equal to the work done in taking it from B to A. If $${W}_{nc}$$ and $${W}_{C}$$ are the work done by non-conservation and conservative force field respectively and $$\Delta U$$ and $$\Delta K$$, be the change in P.E and K.E then
  • $${ W }_{ nc }-\Delta U=\Delta K$$
  • $${ W }_{ C }=-\Delta U$$
  • $${ W }_{ nc }+{ W }_{ C }=\Delta K$$
  • $${ W }_{ nc }=-\Delta U=-\Delta K$$
Two infinitely large sheets having charge densities $$\sigma_1$$ and $$\sigma_2$$ respectively $$(\sigma_1 > \sigma_2)$$ are placed near each other separated by distance '$$d$$'. A small change '$$q$$' is placed in between two plates such that there is no effect on charge distribution on plates. Now this charge is moved at an angle of $$45^o$$ with the horizontal towards plate having charge density $$\sigma_2$$ by distance '$$a$$' $$(a << d)$$. Find the work done by electric field in the process.
1013640_7dd2eebf6ff640429cb54434911040d0.png
  • $$\dfrac{qa(\sigma_1 - \sigma_2)}{5\sqrt{2}\in_0}$$
  • $$\dfrac{qa(\sigma_1 - \sigma_2)}{2\sqrt{2}\in_0}$$
  • $$\dfrac{qa(\sigma_1 - \sigma_2)}{3\sqrt{2}\in_0}$$
  • $$\dfrac{qa(\sigma_1 - \sigma_2)}{4\sqrt{2}\in_0}$$
The position $$x$$ of a particle moving along $$x-$$axis at time $$(t)$$ is given by the equation $$t=\sqrt x+2$$, where $$x$$ is in metres and $$t$$ in seconds. Find the work done by the force in first four seconds.
  • $$Zero$$
  • $$2\ J$$
  • $$4\ J$$
  • $$8\ J$$
The graph below represents the relation between displacement $$x$$ and force $$F$$. The work done in displacing an object from $$x=8\ m$$ to $$x=16\ m$$  is approximately.
1033494_c8a823e1dca0474e96de3e1673455cb1.png
  • $$25\ J$$
  • $$40\ J$$
  • $$8\ J$$
  • $$16\ J$$
The velocity of a body of mass $$20 kg $$ decreases from $$20 m/s $$ to $$ 5 m/s $$ in a distance of $$100 m $$ . Force on the body is :
  • $$ -27.5 N $$
  • $$ -47.5 N $$
  • $$ -37.5 N $$
  • $$ -67.5 N $$
What is the amount of work done in raising a glass of water weighing $$0.5 kg $$ through a height of $$50 cm ? (g = 10 m/s ^2 $$ )
  • $$1 J $$
  • $$ 0.4 J $$
  • $$ 0.20 J $$
  • $$ 2.5 J $$
When a capillary tube of radius r is immersed in a liquid of density $$\rho$$, the liquid rises to a height h in it. If m is the mass of the liquid in the capillary tube, the P.E. of this mass of the liquid in the tube is :
  • $$\cfrac{mgh}{4}$$
  • $$\cfrac{mgh}{2}$$
  • mgh
  • 2mgh
An object of mass $$M_1$$ moving horizontally with speed u collides elastically with another object of mass $$M_2$$ at rest. Select correct statement.
1035459_7b48ab448f464761afb652209a794748.png
  • The momentum of system is conserved only in direction PQ.
  • Momentum of $$M_1$$ is conserved in direction perpendicular to SR.
  • Momentum of $$M_2$$ is conserved in direction perpendicular to CR.
  • All of these
The P.E. of a certain spring certain when stretched from natural length through a distance $$0.3 m $$ is $$10 J$$ . The amount of work in joule that must be done on this spring to stretch it through an additional distance $$0.15 m $$ will be :
  • $$10 J$$
  • $$20 J$$
  • $$7.5 J$$
  • $$12.5 J$$
If increase in linear momentum of a body is 50%, then change in its kinetic energy is
  • 25%
  • 125%
  • 150%
  • 50%
A ball of radius r moving with a speed v collides elastically with another identical stationary ball. The impact parameter for the collision is b as shown in figure.
1076260_c4a17d2c01864f1e9138d55d175835c1.png
  • The balls must scatter at right angles for $$0 < b \le 2r.$$
  • For a head on collision b must be zero, and for an oblique collision $$0
  • After collisions, ball-1 will comes to rest and ball-2 move at an angle $$\sin^{-1} (b/r)$$ below the x-axis
  • After collision ball-1 and 2 will move at angles $$cos^{-1} (b/r) $$and $$\sin^{-1} (b/2r) above and below the x-axis respectively.
In the figure shown initially spring is in uninstructed state & blocks are at rest. Now $$100N$$ force is appiled on block $$A$$ and $$B$$ as shown in figure. After some time velocity of $$'A'$$ becomes $$2m/s$$ and that of $$'B'\ 4m/s$$ and block $$A$$ displaced by amount $$10\ cm$$ and spring is streched by amount $$30\ cm$$. then find the work done by sprig force on $$A$$.
1076999_da7fb5b4d5da4ed6a9f2bb4df7008ee7.png
  • $$9/3\ J$$
  • $$-6\ J$$
  • $$6\ J$$
  • $$-2 J$$
Find the value of $$u$$
1093906_1f299c4bdeb748d09f780086a061e42f.png
  • $$\sqrt{\dfrac{9}{2}Rg}$$
  • $$\sqrt{3Rg}$$
  • $$\sqrt{\dfrac{7}{2}Rg}$$
  • $$\sqrt{7Rg}$$
Two steel spheres approach each other head on with the same speed and collide elastically. After the collision one of the sphere's of radius r comes to rest, the radius of the other sphere is
  • $$\frac{r}{{{{\left( 3 \right)}^{\frac{1}{3}}}}}$$
  • $$\frac{r}{3}$$
  • $$\frac{r}{9}$$
  • $${\left( 3 \right)^{\frac{1}{2}}}r$$

A ball of mass 10 g is projected with an initial velocity of 10 m/s, comes back withd a velocity of 5 m/s at the point of projection. Find the work done by air resistance.(Neglect buoyancy force due to air)
  • 0.375 J
  • 0.275 J
  • -0.375 J
  • Zero
0:0:1


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