CBSE Questions for Class 11 Engineering Physics Laws Of Motion Quiz 9 - MCQExams.com

A cyclist is moving on a circular path with constant speed $$v$$. What is the change in its velocity after it has described an angle of $$30^{o}$$
  • $$v\sqrt{2}$$
  • $$\dfrac{v}{2}$$
  • $$v(0.3\sqrt{3})$$
  • $$None\ of\ these$$
A body is standing on a merry-go-round which is rotating uniformly in a horizontal plane. His frame of reference is 
  • an inertial frame
  • a non- inertial frame
  • either inertial or non- inertial
  • neither inertial nor non- inertial
A ball of mass $$150g$$ moving with an acceleration $$20m/s^2$$ is hit by force , which acts on it for $$0.1sec.$$ The impulsive force is
  • $$0.5$$N-s
  • $$0.1$$N-s
  • $$0.3$$N-s
  • $$30$$N-s
A ball mass 1 kg moving with speed $$10{ ms }^{ -1 }$$ strikers a wall and comes to rest. The impulse of the force on the ball is of magnitude
  • $$5kg{ ms }^{ -1 }$$
  • $$10kg{ ms }^{ -1 }$$
  • $$15kg{ ms }^{ -1 }$$
  • $$20kg{ ms }^{ -1 }$$
The limiting friction between two surfaces does not depend
  • On the nature of two surfaces
  • On normal reaction
  • On the weight of the body
  • on volume of the body
In the state of equilibrium
I) Net force is zero
II) Body at rest will continue to be in its state of rest
III) Body moving with uniform velocity will continue to be in its state of uniform velocity
IV) Body with linear momentum $$\vec{p}$$ will continue to have the same momentum $$\vec{p}$$.
  • All are correct
  • I, II, III are correct
  • II, III, IV are correct
  • None of these
A uniform rod of mass M has an impulse applied at right angles to one end. If the other end begins to move with speed V, the magnitude of the impulse is
  • $$MV$$
  • $$\dfrac {MV} {2}$$
  • $$2MV$$
  • $$\cfrac {2MV} {3}$$
A bod of mass M is suspended by a massless string of length L.The horizontal velocity V at position A is just sufficient to make real the point B.The angle $$\theta$$ at which the speed of the bob is half of that it A satisfies:
1270979_917d575b5ec54ed1b84b2a7ffa04ba11.png
  • $$\theta=\dfrac{\pi}{4}$$
  • $$\dfrac{\pi}{4} < \theta<\frac{\pi}{2}$$
  • $$\dfrac{\pi}{2} < \theta<\dfrac{3\pi}{4}$$
  • $$\dfrac{3\pi}{4} < \theta<\pi$$
A bob is suspended from the ceiling of a car which is accelerating uniformly on a horizontal road
choose the wrong statement
  • the bob stays a constant angle $$\theta$$ with vertical with respect to car in equilibirum
  • the magnitude linear momentum of a bob as seen from the rod is increasing with time
  • linear momentum is conserved only in car reference of frame
  • linear momentum is conserved in car as well as ground reference of frame
Choose the incorrect statement
  • The product of force and time for which it acts is called impulse
  • Change in linear momentum per unit time is called impulse
  • Change in momentum in small interval of time is called impulse
  • Change in linear momentum in a given time is called impulse
Two cubes of size 1.0 m sides, one of relative density 0.60 and another of relative density=1.5 are connected by weightless wire and placed in a large tank of water.Under equilibrium the lighter cube will project above the water surface to a height of:
  • 50 cm
  • 25 cm
  • 10 cm
  • Zero
A body of mass $$M$$ hits normally a rigid wall with velocity $$V$$ and bounces back with the same velocity. The impulse experienced by the body is
  • $$MV$$
  • $$1.5MV$$
  • $$2MV$$
  • zero
The magnitude of the impulse developed by a mass of $$0.2$$kg which changes its velocity from $$5\hat{i}+3\hat{j}+7\hat{k}$$ m/s to $$2\hat{i}+3\hat{j}+\hat{k}$$
  • $$2.7$$N-s
  • $$1.3$$N-s
  • $$0.9$$N-s
  • $$3.6$$N-s
A road is $$10 m $$wide. Its radius of curvature is $$50 m $$. The outer edge is above the lower edge by a distance of $$1./5 m $$. This road is most suited for the velocity
  • $$2.5 m/sec $$
  • $$4.5 m\sec $$
  • $$6.5 m\sec$$
  • $$8.5 m\sec$$
A particle of mass $$m$$ is moving a uniform velocity $${v}_{1}$$. It is given an impulse such that its velocity becomes $${v}_{2}$$. The impulse is equal to
  • $$m\left[ \left| { v }_{ 2 } \right| -\left| { v }_{ 1 } \right| \right] $$
  • $$1/2m[{v}_{1}^{2}-{v}_{1}^{2}]$$
  • $$m[{v}_{1}+{v}_{2}]$$
  • $$m[{v}_{2}-{v}_{1}]$$
If force acting on a system is zero. the quantity which remains constant
  • acceleration
  • linear momentum
  • potential energy
  • Kinetic energy
A particle of mass m is made to move with uniform speed $${ v }_{ 0 }$$ along the perimeter of regular hexagon. The magnitude of impulse at each corner of the hexagon is :
  • $$2{ mv }_{ 0 }sin\dfrac { \pi }{ 6 } $$
  • $${ mv }_{ 0 }sin\dfrac { \pi }{ 6 } $$
  • $${ mv }_{ 0 }sin\dfrac { \pi }{ 3 } $$
  • $$2{ mv }_{ 0 }sin\dfrac { \pi }{ 3 } $$
A particle is moving in a vertical circle. The tension in the string when passing through two positions at angles $${30}^{o}$$ and $${60}^{o}$$ from vertical (lowest position) are $${T}_{1}$$ and $${T}_{2}$$ respectively, then
  • $${T}_{1}={T}_{2}$$
  • $${T}_{2}> {T}_{1}$$
  • $${T}_{1}> {T}_{2}$$
  • tension in the string always remains the same
Two particles of masses $$m_1$$ and $$m_2$$ are moving velocities $$\vec{V_1} $$ and $$\vec { V_2 }  $$ Momentum of the particle of  mass $$m_1$$ with respect to center of mass is 
  • Zero
  • $$\dfrac{m_1 m_2}{m_1 +m_2} (\vec{V_1} -\vec{V_2})$$
  • $$\dfrac{m_2}{m_1 +m_2} (\vec{V_1} - \vec{V_2})$$
  • None of these
A rod of length $$l$$ and mass $$m$$ fixed at one end, it hanging vertically. The other end is now raised so that the rod makes an angle $${30}^{o}$$ with horizontal line. The work done in this process will be:
  • $$3mgl/4$$
  • $$mgl/2$$
  • $$mgl/3$$
  • $$mgl/4$$
A block of mass 200 kg is kept on a rough horizontal surface. It just begins to move when a force of 1000 N is applied. Calculate the coefficient of limiting static friction
  • 0.3
  • 0.4
  • 0.5
  • Insufficient data
An object is subjected to a force in the north-east direction. To balance this force, a second force should be applied in the direction.
  • North - East
  • South
  • South - West
  • West
A glass marble whose mass is 20 gms falls from a height of 0.25 m and rebounds to a height of 1.6 m. If $$g = 9.8 m/s^2$$, find the impulse acting on the fall (in N - s)
  • 0.2
  • 0.4
  • 0.252
  • 0.534
The changes in a momentum of a particle,when the kinetic energy is increased by 0.1% will be:-
  • 0.05%
  • 0.1%
  • 1.0%
  • 10%
Two point masses connected by an ideal string are placed on a smooth horizontal surface as shown in the diagram. A sharp impulse of 10$$\mathrm { kg } \mathrm { mls }$$ is given to the 5$$\mathrm { kg }$$ mass. The velocity of the 10$$\mathrm { kg }$$ mass just after the impulse, will be
  • $$\cfrac { 2 } { 3 } m / s$$
  • $$\cfrac { 1 } { 3 } m / s$$
  • 2$$\mathrm { m } / \mathrm { s }$$
  • zero
The acceleration of a body may be doubled by doubling its:
  • mass
  • momentum
  • velocity
  • force acting on it
The speed of a motor increases from 1200 rpm to 1800 rpm in 20 s. How many revolutions does it make during these second?
  • 400
  • 600
  • 500
  • 700
The tension in the string revolving in a vertical circle with a mass m at the end which is at the lowest position  
  • $$\dfrac{mv^2}{r}$$
  • $$\dfrac{mv^2}{r}-mg$$
  • $$\dfrac{mv^2}{r}+mg$$
  • $$mg$$
When a simple pendulum is rotated in a vertical plane with constant angular velocity, centripetal force is:
  • maximum at highest point
  • maximum at lowest point
  • same at all points
  • zero
A car of mass $$1000 kg$$ moves on a circular path with a constant speed of $$16 m/s$$.It is turned by $${ 90 }^{ \circ  }$$ after traveling $$628 m$$ on the side. The centripetal force acting on the car is -
  • $$160 N$$
  • $$320 N$$
  • $$640 N$$
  • $$1280 N$$
In the figure, at the free end of the light string, a force $$F$$ is applied to keep the suspended mass of $$18 $$\mathrm { kg }$$ at rest. Assuming



1402949_aca715d872ac4b2caeb287507171715b.png
  • $$240 N$$
  • $$120 M$$
  • $$180 M$$
  • $$240 M$$
A cyclist moves along a circular track at 144 km $$h^{-1}$$.What angle must he make with the vertical if the track is 1 km long?
  • $$40^o$$
  • $$45^o$$ 
  • $$35^o$$
  • none
A swing is at 1 m height above ground level in its lowermost position and 3 m in middle position.Its speed at lowest position of vertical circle is-
  • $$ 2 \sqrt{g} $$
  • $$ \sqrt{2g} $$
  • $$ \sqrt {g} $$
  • $$ \sqrt \frac {g}{2} $$
An insect crawls up a hemispherical surface very slowly as shown in the figure. The coefficient of 
friction between the surface and the insect is $$\dfrac { 1 }{ 3 } $$ If the line joining the centre of the hemisphere surface to the insect makes an angle $$\propto $$ with the vertical, the maximum possible value of $$\propto $$ is given by 
1400005_2bc7cc40d8ab4b3296dd9f572cccfc0c.png
  • $$cot\propto =3$$
  • $$tan\propto =3$$
  • $$sec\propto =3$$
  • $$cosec\propto =3$$
A cone filled with water is whirled in a vertical circle of radius 4 m. What will be the time period of rotation so that water does not fall ?
  • 4 s
  • 6 s
  • 2 s
  • 1 s
A track for a certain motor sport event is in the form of a circle and banked at an angle $$\theta$$. For a car driven in a circle of radius r along the track at optimum speed the periodic time is --------
  • $$\sqrt{\dfrac{r}{g}}$$
  • $$ 2 \pi \sqrt{r}{g}$$
  • $$ 2 \pi \sqrt{rg tan \theta}$$
  • $$ 2 \pi \sqrt{\dfrac{g tan \theta}{r}}$$
Three blocks A,B and C are suspended as shown in the figure. Mass of each blocks A and C is m. If system is in equilibrium mass of B is M, then :
1410584_06c9845be22b4a14b5f8fbce6858f072.PNG
  • M=2 m
  • M < 2 m
  • M > 2 m
  • M=m
A ball of mass 1 kg strikes a heavy platform, elastically, moving upward with a velocity of 5 m/s. The speed of the ball just before the collision is 100 m/s downwards. Then the impulse imparted by the platform on the ball is :-
1432670_02e0e1d744ef4824a9a8495e0a537d57.png
  • 15 N-s
  • 10 N-s
  • 20 N-s
  • 30 N-s
The breaking strength of a string is 55 kg wt. The maximum permissible speed of a stone of mass 5 kg which revolved in a vertical circle of radius 4 m with the help of is the string is g=10 $$ {s}^{2} $$.
  • $$

    10 \mathrm{m} / \mathrm{sec}

    $$
  • $$

    15 \mathrm{m} / \mathrm{sec}

    $$
  • $$

    20 \mathrm{m} / \mathrm{sec}

    $$
  • $$

    25 \mathrm{m} / \mathrm{sec}

    $$
Total impulse imposed by ball of mass 2 kg to the ball of mass 4 kg has the magnitude equal to
  • 10 N-s
  • 5.3 N-s
  • 40 N-s
  • 16 Ns
A simple pendulum of length 'l' carries a bob of mass 'm'. If the breaking strength of the string is 2 mg. The maximum angular amplitude from the vertical can be
  • $$

    0^{\circ}

    $$
  • $$3 

    0^{\circ}

    $$
  • $$6 0^{\circ}

    $$
  • $$9

    0^{\circ}

    $$
A gun of mass M fires a bullet of mass m with a velocity v relative to the gun. The average force required to bring the gun to rest in 0.5 sec. is
  • $$

    \dfrac{2 \mathrm{Mmv}}{\mathrm{M}+\mathrm{m}}

    $$
  • $$

    \dfrac{M m v}{2(M+m)}

    $$
  • $$

    \dfrac{3 \mathrm{Mmv}}{2(\mathrm{M}+\mathrm{m})}

    $$
  • $$

    \dfrac{\mathrm{Mmv}}{(\mathrm{M}+\mathrm{m})}

    $$
A ball of mass 250 g moving with 20 m/s strikes a vertical wall and rebounds along the same line with a velocity of 15 m/s. If the time of contact is 0.1 s, the force exerted by the wall on the ball is 
  • $$87.5 N$$
  • $$12.5 N$$
  • $$-12.5 N$$
  • $$-87.5 N$$
Total impulse imposed by a ball of mass $$2 kg$$ moving with the speed of $$10 m/s$$ in rightward direction to the ball of mass $$4 kg$$ moving with the speed of $$8 m/s$$ in the same direction is (The collision is perfectly elastic)
  • $$10 Ns$$
  • $$5.3 Ns$$
  • $$40 Ns$$
  • $$16 Ns$$
Calculate the impulse necessary to stop the car of mass 500 kg travelling at 72 kmph.
  • 10000 Ns
  • 20000 Ns
  • 30000 Ns
  • 40000 Ns
For every action there exists an equal and opposite reaction 
  • True
  • False
An impulse $$\vec { 1 }$$ changes the velocity of a particle from $$\vec { v } _ { 1 }$$ to $$\vec { v } _ { 2 }$$ . Kinetic energy gained by the particle is 
  • $$\frac { 1 } { 2 } \vec { I } \left( \vec { v } _ { 1 } + \vec { v } _ { 2 } \right)$$
  • $$\frac { 1 } { 2 } \vec { I } \left( \vec { v } _ { 1 } - \vec { v } _ { 2 } \right)$$
  • $$\vec { 1 } \cdot \left( \vec { v } _ { 1 } - \vec { v } _ { 2 } \right)$$
  • $$\vec { I } \left( \vec { v } _ { 1 } + \vec { v } _ { 2 } \right)$$
Who asserted that the natural state of body is the state of rest
  • Newton
  • Galileo
  • Aristotle
  • Einstein
A ball of mass $$1$$ $$ \mathrm{kg}  $$ drops vertically on to the floor with a speed of $$ 25$$ $$ \mathrm{m} / \mathrm{s}  $$ . It rebounds with an initial velocity of $$10$$ $$ \mathrm{m} / \mathrm{s}  $$ . What impulse acts on the ball during contact?
  • $$35$$ $$ \mathrm{kg} \mathrm{m} / \mathrm{s} $$ downwards
  • $$35$$ $$ \mathrm{kg} \mathrm{m} / \mathrm{s} $$ upwards
  • $$30$$ $$ \mathrm{kg} \mathrm{m} / \mathrm{s} $$ downwards
  • $$30$$ $$ \mathrm{kg} \mathrm{m} / \mathrm{s} $$ upwards
A rubber ball of mass 50$$\mathrm { g }$$ falls from a height of $$\mathrm { m }$$ and rebounds to a height of .5$$\mathrm { m }$$ . The impulse between the ball and the ground if the time during which they are in contact was $$0,1$$ sec is
  • $$12.5 N - s$$
  • $$11.8 \mathrm { N } - \mathrm { s }$$
  • $$2.36 \mathrm { N } - \mathrm { s }$$
  • $$3.76 \mathrm { N } - s$$
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