CBSE Questions for Class 11 Engineering Physics Laws Of Motion Quiz 10 - MCQExams.com

With what minimum acceleration can a fireman slide down a rope whose breaking strength is two third of his weight ?
  • $$g/2$$
  • $$2g/3$$
  • $$g/3$$
  • $$3g/4$$
An aeroplane flying in the sky with a uniform speed of 200 m/s moves in a vertical circle of radius 400 m. The mass of the pilot is 70 kg. The force exerted by the pilot on the seat at the lowest point on the circle will be
  • 4500 N
  • 6300 N
  • 7700 N
  • 770 N
The minimum speed of a bucket full of water whirled in a vertical circle of radius  $$10 \ m$$  at the highest point so that the water may not fall  $$\left( g = 10 \mathrm { ms } ^ { - 2 } \right)$$
  • $$1 \ ms ^ { -1 }$$
  • $$2 \ ms ^ { -1 }$$
  • $$5 \ ms ^ { -1 }$$
  • $$10 \ ms ^ { -1 }$$
A car running with a velocity 72 kmph on a level road, is stopped after travelling a distance of 30 m after disengaging its engine $$\left( g={ 10ms }^{ -2 } \right) $$. The coefficient of friction between  the road and the tyres is.
  • 0.33
  • 4.5
  • 0.67
  • 0.8
A person wants to drive on the vertical surface of a large cylindrical wooden well commonly known as death well in a circus. The radius of well is R and the coefficient of friction between the tyres of the motorcycle and the wall of the well is $$\mu_s$$. The minimum speed, the motorcyclist must have in order to prevent slipping should be:
  • $$\sqrt{\dfrac{Rg}{\mu_s}}$$
  • $$\sqrt{\dfrac{\mu_s}{Rg}}$$
  • $$\sqrt{\dfrac{\mu_sg}{R}}$$
  • $$\sqrt{\dfrac{R}{\mu_sg}}$$
Impulse indicates.
  • The momentum generated in the direction of force
  • The combined effect of mass and velocity
  • The main characteristics of particle nature
  • Both (b) and (c) are correct
A pendulum bob is held stationary by a horizontal force H. The three forces acting on the bob are shown in the diagram.
The tension in the string of the pendulum is T. The weight of the pendulum bob is W. The string is held at an angle of $$30^o$$ to the vertical.
Which statement is correct?

1648389_088544a651014cb1a8ef99478bd9ad7e.png
  • $$H=T\cos 30$$
  • $$T=H\sin 30$$
  • $$W=T\sin 30$$
  • $$W=T\cos 30$$
The circumference of a circular track is $$400\pi/m$$. If the optimum speed with which a vehicle can be driven along it is to be $$20\ m/s$$, the angle of banking of the road must be about
  • $$\tan^{-1} (0.02)$$
  • $$\tan^{-1} (0.4)$$
  • $$\tan^{-1} (0.8)$$
  • $$\tan^{-1} (0.2)$$
As shown in figure, ball of of mass $$m \,kg$$  is suspended by a string $$\ell \,cm$$ long. Keeping the string always taut, the ball describes a horizontal circle of radius $$\dfrac{\ell}{2}$$. Calculate the angular speed.
1576173_1d09b453431b4f70a8fe50b4dab79948.1576173-Q
  • $$\sqrt{\dfrac{2g}{3\ell}}$$
  • $$\sqrt{\dfrac{2g}{\sqrt{3}\ell}}$$
  • $$\sqrt{\dfrac{3g}{2\ell}}$$
  • None of these
Find the tangent of angle of banking for a curved smooth road of radius  $$40 m$$  for a speed of  $$72 km / h$$   $$\left( { g }=10{ m }/{ s }^{ { 2 } } \right) .$$
  • $$45 ^ { \circ }$$
  • $$37 ^ { \circ }$$
  • $$42 ^ { \circ }$$
  • $$30 ^ { \circ }$$
A road of width $$20$$m forms an arc of radius $$15$$ m, its outer edge is $$2$$m higher than its inner edge. For what velocity the road is banked?
  • $$\sqrt{10}$$ m/s
  • $$\sqrt{14.7}$$ m/s
  • $$\sqrt{9.8}$$ m/s
  • None of these
A rubber band of length $$\lambda$$ has a stone of mass $$m$$ tied to its one end. It is whirled with speed $$v second$$ that the stone described a horizontal circular path. The tension $$T$$ in the rubber band is -
  • zero
  • $$mv^2/\lambda $$
  • $$>(mv^2)/\ell $$
  • none
A cyclist goes round a circular path of length $$400$$m in $$20$$ second. The angle through which he bends from vertical in order to maintain the balance is?
  • $$\sin^{-1}(0.64)$$
  • $$\tan^{-1}(0.64)$$
  • $$\cos^{-1}(0.64)$$
  • None of these
Mark correct option or options.
  • The body of greater mass needs more forces to move due to more inertia
  • Force versus time graph gives impulse
  • Microscope area of contact is about $$10^{-4}$$ times actual area of the contact
  • All of the above
If a number of forces act on a body and the body is in static of dynamic equilibrium then
  • Work done by any individual force must be zero
  • Net work done by all the forces is positive
  • Net work done by all the forces is negative
  • Net work done by all the forces is zero
If $$F = F_{0} (1 - e^{-t/\lambda})$$, the $$F-t$$ graph is
In the figure, a block of weight $$60\ N$$ is placed on a rough surface. The coefficient of friction between the block and the surfaces is $$0.5$$. What minimum can be the weight $$W$$ such that the block does not slip on the surface?
1734545_e08182f13cd0481b9eddd1fbef7ade3a.png
  • $$60\ N$$
  • $$\dfrac{60}{\sqrt 2}N$$
  • $$30\ N$$
  • $$\dfrac{30}{\sqrt 2}N$$
Consider the situation shown in the figure. The wall is smooth but the surfaces of $$A$$ and $$B$$ in contact are rough. Then
1702819_157222fd88d34e8c808620aab78b8b05.png
  • System may remain in equilibrium
  • Both bodies must move together
  • The system cannot remain in equilibrium
  • None of the above
A ring of mass $$5\ kg$$ sliding on a frictionless vertical rod is connected by a block $$B$$ of mass $$10\ kg$$ by the help of a massless string. Then at the equilibrium of the system the value of $$\theta$$ is
1702532_d5eaa5a1f30140d1ad02aab1b65386af.png
  • $$30^{\circ}$$
  • $$60^{\circ}$$
  • $$90^{\circ}$$
  • $$0^{\circ}$$
At time $$t$$ second, a particle of mass $$3\ kg$$ has position vector $$\vec {r}$$ metre where $$\vec {r} = 3t\hat {i} - 4\cos t \hat {j}$$. The impulse of the force during the time interval $$0 < t < \dfrac {\pi}{2}$$ is
  • $$12\hat {j} N-s$$
  • $$9\hat {j} N-s$$
  • $$4\hat {j} N-s$$
  • $$14\hat {j} N-s$$
In the given figure, pulleys and strings are massless. For equilibrium of the system, the value of $$\alpha$$ is
1702531_443765b17bf6417595f9b67d143c8dcc.png
  • $$60^{\circ}$$
  • $$30^{\circ}$$
  • $$90^{\circ}$$
  • $$120^{\circ}$$
A $$0.1\ kg$$ body moves at a constant speed of $$10\ m/s$$. It is pushed by applying a constant force for $$2\sec$$. Due to this force, it starts moving exactly in the opposite direction with a speed of $$4\ m/s$$. Then
  • The deceleration of the body is $$7\ m/s^{2}$$
  • The magnitude of change in momentum is $$1.4\ kg-m/\sec$$
  • Impulse of the force is $$1.4\ Ns$$
  • The force which acts on the ball is $$0.7\ N$$
  • All of the above
 In the arrangement shown below, the thread pulley and spring are all massless and there is no friction anywhere. The system is in equilibrium. If the thread connecting $$ m_4 $$ is cut then just after the thread is cut :
1742709_581af00a95f54ce2896cb09f85481686.png
  • acceleration of $$ m_4 = 0 $$
  • acceleration of $$ m_1 = m_2 = m_3 = m_4 = 0 $$
  • acceleration of $$ m_1 = m_1 = m_3 = 0$$
  • acceleration of $$ m_4 = \frac { [ ( m_1 +m_2) -) m_3 +m_4 ) ] g }{ m_4} $$
Consider the system as shown. The wall is smooth, but the surface of block A & B in contact is rough. the friction force on B due to A is equilibrium is:
1741993_560dbae1a514429d8e3fde327d5aa677.png
  • Zero
  • Upwards
  • Downwards
  • The system can not remain in equilibrium
A smooth circular road of radius r is banked for a speed v = 40 km/hr . A car of mass m attempts to go on the circular road. The friction coefficient between the tyre and the road is negligible . the correct statements are : 
  • The car cannot make a tum without skidding.
  • If the car turns at a speed less than 40 km/hr, it slips down
  • If the car turns at the correct speed of 40 km/hr, the force by the road on the car is equal to $$ mv^2 / r $$
  • If the car turns at the correct speed of 40 km/hr, the force by the road on the car is greater than mg as well as greater than $$ mv^2 / r $$
Four bricks, each of length l, are put on the top of one another in such a way that part of each extends beyond the one beneath. For the largest equilibrium extensions,
1735845_c0979d9d75b64870a1c533628bcb030d.PNG
  • The top brick overhanging the one below by $$l/4$$
  • The second brick from top over hanging the one below by $$l/4$$
  • The third brick from top overhanging the bottom one by $$l/6$$
  • The total overhanging length on the edge of the bottom brick is $$(11/12)l$$
A particle of mass $$2$$ kg moving with a velocity of $$3$$ m/s is acted upon by a force which changes its direction of motion by an angle of $$90^o$$ without changing its speed. What is the magnitude of impulse experienced by the particle?
  • $$6$$ N s
  • $$2$$ N s
  • $$3\sqrt{2}$$ N s
  • $$6\sqrt{2}$$ N s
A system of two blocks A and B are connected to an inextensible massless string as shown in Fig. The pulley is massless and frictionless. Initially, the system is at rest. A bullet of mass 'm' moving with a velocity 'u' as shown hits block 'B' and gets embedded into it. The impulse imparted by tension force to the block of mass $$3m$$ is?
1735473_da38910a238b457e87f9da7f7d40d47b.PNG
  • $$\dfrac{5mu}{4}$$
  • $$\dfrac{4mu}{5}$$
  • $$\dfrac{2mu}{5}$$
  • $$\dfrac{3mu}{5}$$
Three blocks A, B and C are suspended as shown below. mass of each of block A and B is m . if the system is in equilibrium , and mass of C is M then :  
1741778_8ad69d113c7344e4b5adabf73baad93f.png
  • $$ M < 2 m $$
  • $$ M > 2 m $$
  • $$ M = 2 m $$
  • $$ M \le 2 m $$
Two particles A & B each of mass  m are in equilibrium in a vertical plane under action of a horizontal force F = mg on the particle B , as shown in figure then : 
1742725_0452a55cc5084c28a691b3713ef94106.PNG
  • $$ 2 T_1 = 5T_2 $$
  • $$ T_1 \sqrt {2} = T_2 \sqrt {5} $$
  • $$ tan \theta = 2 tan \alpha $$
  • None of these
A curved section of a road is banked for a speed v. If there is no friction between road and tyre Then :
  • a car moving with speed v will not slip on road
  • a car is more likely to slip on the road at speed higher than v, than at speeds lower than v
  • a car is move likely to slip on the road at speed lower than v , than at speeds higher than v
  • a car cannot remain stationary on road and will start slipping
Which of the following is / are incorrect: 
  • If net normal force on a surface is zero, friction will be zero
  • value of static friction is given by $$ \mu_5 N $$
  • Static friction opposes relative motion between two surfaces is conatct
  • kinetic friction reduces velocity of an object
Write true or false for the following statements:
Impulse represents the rate of change of momentum of a body.
  • True
  • False
The momentum of a body of given mass is proportional to its:
  • speed
  • volume
  • density
  • shape
A force always produces both linear and turning motions.
  • True
  • False
For a given thrust, pressure is more on a surface of large $$ j$$ area
  • True
  • False
A cricket ball of mass150g has the initial velocity $$\vec u = (3 \hat{i}+  4\hat{j}) ms^{-1} $$  and a   final  velocity $$\vec v = -(3\hat {i}+4\hat{j} ) ms^{-1}$$     after being hit.The change in momentum (final momentum–initial momentum) is(inkg $$ms^{-1}$$)
  • Zero
  • $$(-0.45 \hat{i} + 0.6\hat{j})$$
  • $$(-0.9\hat{i} - 1.2\hat{j})$$
  • $$-5(\hat {i} + \hat {j})$$
The maximum velocity at the lowest point, so that the string just slack at the highest point in a vertical circle of radius l
  • $$\sqrt{gl}$$
  • $$\sqrt{3gl}$$
  • $$\sqrt{5gl}$$
  • $$\sqrt{7gl}$$
The unit of linear momentum is :
  • $$Ns$$
  • $$kg ms^{-2}$$
  • $$Ns^{-1}$$
  • $$kg^{2} ms^{-1}$$
An aircraft is moving with a velocity of $$300 \ ms^{-1}$$. If all the forces
acting on it are balanced, then 
  • It still moves with the same velocity
  • It will be just floating at the same point in space
  • It will fall down instantaneously
  • It will lose its velocity gradually
  • It will explode
A ball is moving to and fro about the lowest point A of a smooth hemispherical bowl. If it is able to rise up to a height of 20 cm on either side of A, its speed at A must be
  • $$0.2 \,m/s$$
  • $$2 \,m/s$$
  • $$4 \,m/s$$
  • $$4.5 \,m/s$$
Roads are banked on curves so that
  • The speeding vehicles may not fall outwards
  • The frictional force between the road and vehicle may be decreased
  • The wear and tear of tyres may be avoided
  • The weight of the vehicle may be decreased
Maximum value of static friction is called.
  • Limiting friction
  • Rolling friction
  • Normal reaction
  • Coefficient of friction
The limiting friction is
  • Always greater than the dynamic friction
  • Always less than the dynamic friction
  • Equal to the dynamic friction
  • Sometimes greater and sometimes less than the dynamic friction
A rocket is propelled by a gas which is initially at a temperature of $$4000 \ K$$. The temperature of the gas falls to $$1000 \ K$$ as it leaves the exhaust nozzle. The gas which will acquire the largest momentum
while leaving the nozzle is
  • Hydrogen
  • Helium
  • Nitrogen
  • Argon
Unit of momentum is:
  • Newton metre
  • Newton kg/ metre
  • Newton metre/ sec
  • Newton sec
What is product of force and the time for which force act called?
  • Momentum
  • Acceleration
  • Inertia
  • Impulse of force
What is the momentum of an object of mass m, moving with a velocity $$V$$ ?
  • $$(mV)^{2}$$
  • $$mV^{2}$$
  • $$\frac{1}{2}mV^{2}$$
  • $$mV$$
Two forces are acting on an object. Which of the following statements is correct?
  • The object is in equilibrium if the forces are equal in magnitude and opposite in direction.
  • The object is in equilibrium if the net torque on the object is zero.
  • The object is in equilibrium if the forces act at the same point on the abject.
  • The object is in equilibrium if the net force and the net torque on the object are both zero.
  • The object cannot be in equilibrium because more than one force acts on it.
An ice cube has been given a push and slides without friction on a level table. Which is correct?
  • It is in stable equilibrium.
  • It is in unstable equilibrium.
  • It is in neutral equilibrium.
  • It is not in equilibrium.
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