CBSE Questions for Class 11 Engineering Physics Work,Energy And Power Quiz 8 - MCQExams.com

A particle of mass m strikes a wall at an a wall at angle of incidence $$60^o$$ with velocity v elastically. The change in momentum is:
  • $$mv$$
  • $$m v/2$$
  • $$-2 m v$$
  • $$Zero$$
A stone of mass $$1\ kg$$ is tied to a string $$4\ m$$ long and is rotated at constant speed of $$40\ ms^{-1}$$ in a vertical circle. The ration of the tension at the top and the bottom is
  • 11:12
  • 39:41
  • 41:39
  • 12:11
A ball is dropped from certain height, after striking the gourn it rebounds till $$\frac{2}{5}th$$ of the initial height. The ration of its speed just before and just after striking the ground is [assume no loss of energy due to air friction]
  • $$\sqrt{\dfrac{2}{5}}$$
  • $$\dfrac{2}{5}$$
  • $$\sqrt{\dfrac{5}{2}}$$
  • $$\dfrac{5}{2}$$
A force acts on a $$30 gm$$ particle in such a way that the position of the particle as a function of time is given by $$x=3t-4{t}^{2}+{t}^{3}$$, where $$x$$ is in metres and $$t$$ is in seconds. The work done on the particle during the first $$4$$ second is  
  • $$3.84J$$
  • $$1.68J$$
  • $$5.28J$$
  • $$5.41J$$
A horizontal $$50\ N$$ force acts on a $$2\ kg$$ crate which is at rest on a smooth horizontal surface. At the instant the particle has gone $$2\ m$$, the rate at which the force is doing work is
  • $$2.5\ W$$
  • $$25\ W$$
  • $$100\ W$$
  • $$500\ W$$
Circular flexible current loop of radius R carrying current I is placed in an inward magnetic field B. If we spin the loop with angular speed $$/omega $$, then tension in string
  • Is zero
  • is more than iBR
  • is less than iBR
  • Does not depend on rotation
A body covers a distance of $$4m$$ under the action of force $$F=\left( 17-4x \right) N$$ where x is the metres. The work done by the force is
  • $$32J$$
  • $$20J$$
  • $$36J$$
  • None
A particle is projected on friction less inclined plane of inclination $$90^{\circ}$$ from the horizontal, with the projection angle $$45^{\circ}$$ from the inclined plane as shown in the figure. After one collision from the plane. It reaches to its initial point of projection. Coefficient of restitution between particle and plane is
  • $$\frac{2}{3}$$
  • $$\frac{1}{3}$$
  • $$\frac{3}{25}$$
  • $$\frac{1}{\sqrt{2}}$$
When two springs A and B with force constant $$ K_A and K_B $$ are stretched by same force,the respective work done on them is:
  • $$ K_B : K_A $$
  • $$ K_A : K_B $$
  • $$ K_A K_B :1 $$
  • $$ \surd K\_ 4:\surd K\_ B $$
Two particles A and B equal masses are respectively tied to the centre and one end of a string, whose other end 0 is fixed. Both the particles always revolve in concentric circles of centre O. The ratio of tensions in both the parts of the string will be
1128029_ac65991013d441e38cfddedc1330b2f6.png
  • 3:2
  • 2:3
  • 1:2
  • 1:1
A particle moves along the x- axis from x=0 to x=5 m under the influence of a force given by $$F=7-2x+3x^2$$.Work done in the process is 
  • 70
  • 270
  • 35
  • 135
The disc is at rest at the top of a rough inclined plane. It rolls without slipping. At the bottom of inclined plane there is a vertical groove if radius $$R$$. In order to loop the groove, the minimum height of incline required is:
  • $$\dfrac{15 R}{4}$$
  • $$\dfrac{9 R}{4}$$
  • $$\dfrac{5 R}{2}$$
  • $$\dfrac{7 R}{5}$$
The force required to stretch a spring varies with the distance as shown in the figure. If the experiment is performed with the above spring of half the length, the line $$OA$$ will:-
1130255_410a7d891ac44608bd7ee5be43a10857.png
  • shift towards $$F-$$axis
  • shift towards $$X-$$axis
  • remains as it is
  • become double in length
A time dependent force F = 6t acts on a particle of mass 1 kg. If the particle starts from set, the work done by the force during the first 1 sec. will be :
  • 22 J
  • 9 J
  • 18 J
  • 4.5 J
Identify the wrong statement
  • A body can have momentum without energy
  • A body can have energy without momentum
  • the momentum is conserved in an elastic collision
  • Kinetic energy is not conserved in an inelastic collision
If two balls each of mass 0.06 Kg moving in opposite directions with speed 4 m/sec collides and rebound with the same speed,then coefficient of restitution for the collision will be:-
  • $$ \frac { 1 }{ 4 } $$
  • $$\frac { 1 }{ 2} $$
  • 1
  • 0
A $$10$$ kkg object attached to a nylon cord outside a space vehicle is rotating at a speed of $$5 m/s$$. If the force acting on the cord is $$125 N$$ its radius of path is 
  • 2 m
  • 4 m
  • 6 m
  • 1 m
A gun fires a shell of mass $$1.5 $$kg with velocity of $$150$$ m/s and recoils with a velocity of $$2.5$$ m/s. 
Calculate the mass of the gun.
  • $$20$$ kg
  • $$30$$ kg
  • $$90$$ kg
  • $$60$$ kg
A spring of natural length $$L$$ compressed to length $$7\ L/8$$ exerts a force $$F_0$$. The work done by the spring in restoring itself to natural length is 
  • $$F_0\ L/25$$
  • $$F_0\ L/16$$
  • $$3F_0\ L/25$$
  • $$F_0\ L/8$$
The $$P.E.$$ and $$K.E.$$ of a helicopter flying horizontally at a height $$400\ m$$ are in the ratio $$5:2$$. The velocity of the helicopter is:
  • $$56\ m/s$$
  • $$28\ m/s$$
  • $$14\ m/s$$
  • $$42\ m/s$$
At the instant t= 0 a force F=kt( k is a constant) acts on a small body of mass m resting on a smooth horizontal surface.The time,when body leaves the surface is:
  • $$mg\ k \ sin \alpha $$
  • $$\dfrac{k }{mg \ sin \alpha}$$
  • $$\dfrac{mg \ sin \alpha}{k }$$
  • $$\dfrac{mg}{k \ sin \alpha}$$
A body of mass tied at the end of a strong of length $$l$$ is projected with velocity $$\sqrt{4lg}$$, at what height will it leave the circular path:
  • $$\dfrac{5}{3}l$$
  • $$\dfrac{3}{5}l$$
  • $$\dfrac{1}{3}l$$
  • $$\dfrac{2}{3}l$$
A ball of mass m approaches a wall of mass M (>> m) with the speed 4 m/s along normal to the wall. The speed of wall is 1m/s towards the ball . The speed of the ball after an elastic collision with the wall is-
  • 5 m/s away from the wall
  • 3 m/s away from the wall
  • 9 m/s away from the wall
  • 6 m/s away from the wall
A ball falls from a height such that it strikes the floor of lift at $$10\ m/s$$, if lift is moving in the upward direction with a velocity $$1\ m/s$$ , then velocity with the ball rebounds after elastic collision will be then
  • $$11\ m/s$$
  • $$12\ m/s$$
  • $$13\ m/s$$
  • $$9\ m/s$$
The length of simple pendulum is 1 m and mass of its bob is 50 g. The bob is given sufficient velocity so that the bob describe vertical circle whose radius equal to length of pendulum. The maximum difference in the kinetic energy of bob during one revolution is.
  • 0.98 J
  • 1.96 J
  • 4.9 J
  • 9.8 J
A particle is acted upon by a force F which varies with position x as shown in the figure. If the particle at $$x=0$$ has the kinetic energy of $$25$$ J, then the kinetic energy of the particle at $$x=16$$m is?
1208470_a40f7e31514246c2ad656b86645125c1.png
  • $$45$$J
  • $$30$$J
  • $$70$$J
  • $$135$$J
When a spring is stretched by a distance $$x,$$ it exerts a force given by $$F$$ $$=$$ ($$ -5x - 16x^3$$) $$N,$$ where $$x$$ is in $$m.$$ The work done, when the spring is stretched from $$0.1\ m$$ to $$0.2\ m$$ is :
  • $$6.9\times 10^{-2}\ J$$
  • $$12.2 \times 10^{-2}\ J$$
  • $$8.1 \times 10^{-2}\ J$$
  • $$12.2 \times 10^{-1}\ J$$
The work done by a force $$\vec{F}=\left ( -6x^3\hat{i} \right )\ N$$ is displacing a particle from $$x=4\ m$$ to $$x=-2\ m$$ is

  • $$-240\ J$$
  • $$360\ J$$
  • $$120\ J$$
  • $$420\ J$$
Velocity-time graph of a particle of mass $$2\,\,kg$$ moving in a straight line as shown in figure. Work done by all the forces on the particle is :
1206603_ac526021192a4099a07c75ae23d91baa.png
  • $$400\,J$$
  • $$- 400\,J$$
  • $$- 200\,J$$
  • $$200\,J$$
A body of mass $$6\,kg$$  is under a force which causes displacement in it given by $$S = \dfrac{{{t^2}}}{4}$$  metres where $$t$$ is time. The work done by the force in $$2$$ seconds is:-
  • $$12\,J$$
  • $$9\,J$$
  • $$6\,J$$
  • $$3\,J$$
A light particle moving horizontally with a speed of $$12\ m/s$$ strikes a very heavy block moving in the same direction at $$10\ m/s$$. The collision is one-dimensional and elastic. If the speed of the block does not change after the collision, the particle will
1209463_0a3c7af683594f95823cca5c0be037db.png
  • Move at $$2\ m/s$$ in its original direction
  • Move at $$8\ m/s$$ in its original direction
  • Move at $$8\ m/s$$ opposite to its original direction
  • Move at $$12\ m/s$$ opposite to its original direction
Find the reading of machine. Given each box of mass$$=15 kg$$,mass of man $$ 1=30kg$$, mass of man $$2=40 kg$$ and of each weighing machine $$=5 kg$$
1190764_47b1e62228974051a1e4cd887bbca763.PNG
  • $$360/11 kg, 400/11 kg $$
  • $$330/11 kg, 440/11 kg $$
  • $$360/11 kg, 440/11 kg $$
  • $$350/11 kg, 240/11 kg $$
When a massive body suffers an elastic collision with a stationary light body, then massive body approximately comes to rest and light body- 
  • acquires velocity greater than initial velocity of massive body
  • sticks to the massive body and remains at rest.
  • acquires half the initial velocity of the massive body
  • remains at rest but does not stick to the massive body.
Five equal force of $$10$$N each applied at one point and all are lying in one plane. If the angles between them are equal, the resultant force will be
  • zero
  • $$10$$N
  • $$20$$N
  • $$10\sqrt2$$
A body is moving along y-axis and force acting on it is given by F = sin Ky, where K is a constant . The work done by the force from y = 0 to y = 1 is 
  • $$\dfrac { 1 }{ K(1-sinK) } $$
  • $$\dfrac { { 2sin }^{ 2 }\dfrac { K }{ 2 } }{ K } $$
  • $$\dfrac { cosK-1 }{ K } $$
  • cos K - 1
A force $$F = -kx^3$$ is acting on a block moving along x-axis. Here, k is a positive constant. Work done by this force is:
  • positive in displacing from x = 3 to x = 1
  • positive in displacing from x = -1 to x = 3
  • negative in displacing from x = 3 to x = 1
  • negative in displacing from x = -1 to x = 3
A body of mass 'M' collides against a wall with a velocity v and retraces its path with the same speed. the change in momentum is ............. (take initial direction of velocity as positive)
  • Zero
  • 2Mv
  • Mv
  • -2 Mv
A force $$F=Kx^{2}$$ acts on a particle at angle of $$60^{o}$$ with $$x-$$ axis. The work done in displacing the particle from $$x_{1}$$ to $$x_{2}$$ will be:
  • $$\dfrac{kx^{2}}{2}$$
  • $$\dfrac{k}{6}(x_{3}^{2}-x_{1}^{3})$$
  • $$\dfrac{k}{2}(x_{2}^{3}-x_{1}^{3})$$
  • $$\dfrac{k}{3}(x_{2}^{3}-x_{1}^{3})$$
Gravel is dropped on a conveyor belt at the rate of $$2kg/s$$. The extra force required to keep the belt moving at $$3 ms^{-1}$$ is
  • $$1 N$$
  • $$3 N$$
  • $$4N$$
  • $$6 N$$
A car is travelling at 5 m/s up a gradient of 1 inThe car weight 6 tonnes and the friction is 48 kg wt. The work done per second in maintaining the motion of car up the gradient is $$(g=10ms^{-2}$$)
  • 12400 W
  • 1362 W
  • 17400 W
  • 1520 W
A spring with spring constant $$k$$ is extended from $$x=0$$ to $$x={x}_{1}$$. The work done will be
  • $${kx}_{1}^{2}$$
  • $$\dfrac{1}{2}{kx}_{1}^{2}$$
  • $$2{kx}_{1}^{2}$$
  • $$2{kx}_{1}$$
A force acts on a $$20g$$ particle in such a way that the position of the particle as a function of time is given by $$x=3t-4t^2+t^3$$, where x is in meters and $$t$$ is in seconds. The work done during the  first $$4sec$$ is:
  • $$-1.6J$$
  • $$-1600J$$
  • $$2.6 J$$
  • $$1600J$$
If a resultant force of $$30N$$ acts on a body of mass $$6kg$$.What is the acceleration of the body?
  • $$20m/sec^2$$
  • $$12m/sec^2$$
  • $$5m/sec^2$$
  • $$8m/sec^2$$
A body of mass $$5 kg$$ under a force which causes displacement in it given $$S=\dfrac{t^2}{4}$$ meter where $$'t'$$ is time. The work done by the force in $$4 seconds$$ is:
  • $$12J$$
  • $$20 J$$
  • $$2.55 J$$
  • $$10 J$$
A force of $$F = 2x\hat{i} + 2\hat{j} + 3z^{2}\hat{k} N$$ is acting on a particle. Find the work done by this force in displacing the body from (1,2,3) into (3,6,1) m.
  • $$-10 J$$
  • $$100$$
  • $$10 J$$
  • $$1 J$$
When the mass of body is halved and velocity is doubled, then the kinetic energy of the body 
  • remains same
  • is doubled
  • is 4 times
  • is $$\frac{1}{4}$$ th
A force $$F=Ay^{2}+By+C$$ acts on a body in the $$y$$ direction, The work done by this force during a displacement from $$y=-a$$ to $$y=a$$ is
  • $$\dfrac{2Aa^{2}}{3}$$
  • $$\dfrac{2Aa^{2}}{3}+2Ca$$
  • $$\dfrac{2Aa^{2}}{3}+\dfrac{Ba^{2}}{2}+Ca$$
  • $$None\ of\ these$$
A body of mass $$15\ kg$$ moving with a velocity of $$10\ ms^{-1}$$ is bought to rest. The work done by the brake is
  • $$-250\ J$$
  • $$-500\ J$$
  • $$-750\ J$$
  • $$-1000\ J$$
A ball of mass $$5$$ kg experiences a force $$F=2x^{2}+x$$. Work done in displacing the ball by $$2$$ m is 
  • $$22/3$$ J
  • $$44/3$$ J
  • $$32/3$$ J
  • $$16/3$$ J
A body of mass 0.5 kg travels in a straight line with velocity $$v=ax^{3/2}$$ where $$a=5m^{-1/2}s^{-1}$$. the work done by the net force during its displacement from $$x=0$$ to $$x=2m$$ is  
  • $$1.5J$$
  • $$50J$$
  • $$10J$$
  • $$100J$$
0:0:1


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