JEE Questions for Physics Laws Of Motion Quiz 9 - MCQExams.com

A block of mass m is resting on a smooth horizontal surface. One end of a uniform rope of mass (m/is fixed to the block, which is pulled in the horizontal direction by applying a force F at the other end. The tension in the middle of the rope is

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  • 0°
  • 30°
  • 45°
  • 90°
A pulse of light of duration 100 ns is absorbed completely by a small object initially at rest. Power of the pulse is 30 m W and the speed of light is 3 × 108m/s.The final momentum of the object is
  • 0.3 × 10–17 kg ms–1
  • 1.0 × 10–17 kg ms–1
  • 3.0 × 10–17 kg ms–1
  • 9.0 × 10–17 kg ms–1
A force of 5 N acts on a body of weight 9.8 N. What is the acceleration produced in m/s2?
  • 49.00
  • 5.00
  • 1.46
  • 0.51
The engine of a car produces acceleration 4 m/s2 in the car. If this car pulls another car of same mass, what will be the acceleration produced?
  • 8 m/s2
  • 2 m/s2
  • 4 m/s2
  • 1/2 m/s2
A rope of length 5 m is kept on frictionless surface and a force of 5 N is applied to one of its end. Find tension inthe rope at lm from this end
  • 1 N
  • 3 N
  • 4 N
  • 5 N
A lift is going up. The total mass of the lift and the passenger is 1500 kg. The variation in the speed of the lift is as given in the graph. The tension in the rope pulling the lift at t =11th s will be
Physics-Laws of Motion-77207.png
  • 17400 N
  • 14700 N
  • 12000 N
  • Zero
In the above question, the height to which the lift takes the passenger is
  • 3.6 m
  • 8 m
  • 1.8 m
  • 36 m
A body of mass 5 kg is suspended by a spring balance on an inclined plane as shown in figure. The spring balance measure
Physics-Laws of Motion-77210.png
  • 50 N
  • 25 N
  • 500 N
  • 10 N
For ordinary terrestrial experiments, the observer is an inertial frame in the following cases is
  • A child revolving in a giant wheel
  • A driver in a sports car moving with a constant high speed of 200 km h–1 on a straight road
  • The pilot of an aeroplane which is taking off
  • A cyclist negotiating a sharp curve
A particle of mass 0.3 kg is subjected to a force F = –kx with k = 15 N/m. What will be its initial acceleration if it is released from a point 20 cm away from the origin?
  • 5 m/s2
  • 10 m/s2
  • 3 m/s2
  • 15 m/s2
Which of the following quantities measured from different inertial reference frames are same?
  • Force
  • Velocity
  • Displacement
  • Kinetic energy
Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows along the road with velocity w. One of these vehicles blows a whistle of frequency f1. An observer in the other vehicle hears the frequency of the whistle to be f2. The speed of sound in still air is v. The correct statement(s) is (are)
  • If the wind blows from the observer to the source, f2 > f1
  • If the wind blows from the source to the observer, f2 < f1
  • If the wind blows from observer to the source, f2 < f1
  • If the wind blows from the source to the observer, f2 < f1
A solid disc of mass M is just held in air horizontally by throwing 40 stones per sec vertically upwards to strike the disc each with a velocity 6 ms–1. If the mass of each stone is 0.05 kg. What is the mass of the disc?(g = 10 ms–2)
  • 1.2 kg
  • 0.5 kg
  • 20 kg
  • 3 kg
If a body of mass m is carried by a lift moving with an upward acceleration a, then the forces acting on the body are (i) the reaction R on the floor of the lift upwards (ii) the weight mg of the body acting vertically downwards. The equation of motion will be given by
  • R = mg – ma
  • R = mg + ma
  • R = ma – mg
  • R = mg × ma
A force of 100 dyne acts on a mass of 5 g for 10 s. Thevelocity produced is
  • 2000 cm/s
  • 200 cm/s
  • 20 cm/s
  • 2 cm/s
A boy having a mass equal to 50 kilograms is standing in an elevator. The force felt by the feet of the boy will be greatest when the elevator(g=9.8m/s2)
  • Stands still
  • Moves downward at a constant velocity of 4 m/s
  • Accelerates downward with an acceleration equal to 4 m/s2
  • Accelerates upward with an acceleration equal to 4 m/s2
There is a simple pendulum hanging from the ceiling of a lift. When the lift is stand still, the time period of the pendulum is T. If the resultant acceleration becomes g / 4, then the new time period of the pendulum is
  • 0.8 T
  • 0.25 T
  • 2 T
  • 4 T
The ratio of the weight of a man in a stationary lift and when it is moving downward with uniform acceleration \'a \' is 3 : 2. The value of \'a\' is (g-Acceleration due to gravity of the Earth)

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The spring balance inside a lift suspends an object. As the lift begins to ascend, the reading indicated by thespring balance will
  • Increase
  • Decrease
  • Remain unchanged
  • Depend on the speed of ascend
In an elevator moving vertically up with an acceleration g, the force exerted on the floor by a passenger of mass M is
  • Mg
  • 1/2Mg
  • Zero
  • 2 Mg
A mass 1 kg is suspended by a thread it is
(i) lifted up with an acceleration 4.9 m/s2
(ii) lowered with an acceleration 4.9 m/s2.
The ratio of the tensions is
  • 3 : 1
  • 1 : 3
  • 1 : 2
  • 2 : 1
The time in which a force of 2 N produces a change in momentum of 0.4 kg ms–1 in the body is
  • 0.2 s
  • 0.02 s
  • 0.5 s
  • 0.05 s
A cork is submerged in water by a spring attached to the bottom of a pail. When the pail is kept in a elevator moving with an acceleration downwards, the spring length
  • Increases
  • Decreases
  • Remains unchanged
  • Data insufficient
A ball of mass 400 g is dropped from a height of 5 m. A boy on the ground hits the ball vertically upwards with a bat with an average force of 100 N so that it attains a vertical height of 20 m. The time for which the ball remains in contact with the bat is [g = 10 m/s2]
  • 0.12 s
  • 0.08 s
  • 0.04 s
  • 12 s
The linear momentum p of a body moving in one dimension varies with time according to the equation p = a + bt2, where a and b are positive constants. Thenet force acting on the body is
  • A constant
  • Proportional to t2
  • Inversely proportional to t
  • Proportional to t
A body is imparted motion from rest to move in a straight line. If it is then obstructed by an opposite force, then
  • The body may necessarily change direction
  • The body is sure to slow down
  • The body will necessarily continue to move in the same direction at the same speed
  • None of the above
The adjacent figure is the part of a horizontally stretched net. Section AB is stretched with a force of 10 N. The tensions in the sections BC and BF are
Physics-Laws of Motion-77229.png
  • 10 N, 11 N
  • 10 N, 6 N
  • 10 N, 10 N
  • Cannot calculate due to insufficient data
A second pendulum is mounted in a rocket. Its period of oscillation decreases when the rocket
  • Comes down with uniform acceleration
  • Moves round the earth in a geostationary orbit
  • Moves up with a uniform velocity
  • Moves up with uniform acceleration
A particle moves in the xy–plane under the action of a force Fsuch that the components of its linear momentum p at any time t are px = 2 cost, py = 2 sin t. The angle between F and p attime t is
  • 90°
  • 0°
  • 180°
  • 30°
A cricket ball of mass 250 g collides with a bat with velocity 10 m/s and returns with the same velocity within 0.01 s. The force acted on bat is
  • 25 N
  • 50 N
  • 250 N
  • 500 N
A pendulum bob of mass 50 g is suspended from the ceiling of an elevator. The tension in the string if the elevator goes up with uniform velocity is approximately
  • 0.30 N
  • 0.40 N
  • 0.42 N
  • 0.50 N
A ball of mass 0.5 kg moving with a velocity of 2 m/s strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and the wall is 1 ms, the average force exerted by the wall on the ball is
  • 2000 N
  • 1000 N
  • 5000 N
  • 125 N
An automobile travelling with a speed of 60 km/h, can brake to stop within a distance of 20 m. If the car is going twice as fast, i. e., 120 km/hr, the stoppingdistance will be
  • 20 m
  • 40 m
  • 60 m
  • 80 m
A ball of mass m moves with speed v and it strikes normally with a wall and reflected back normally, if its time of contact with wall is t, then find force exerted byball on wall

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A plumb line is suspended from a ceiling of a car moving with horizontal acceleration of a. What will be the angle of inclination with vertical?
  • tan–1(a/g)
  • tan–1(g/a)
  • cos–1(a/g)
  • cos–1(g/a)
A force of 10 N acts on a body of mass 20 kg for 10 s.Change in its momentum is
  • 5 kg m/s
  • 100 kg m/s
  • 200 kg m/s
  • 1000 kg m/s
A body of mass 1.0 kg is falling with an acceleration of 10 m/s2. Its apparent weight will be (g = 10 m/s2)
  • 1.0 kg
  • 2.0 kg
  • 0.5 kg
  • Zero
A lift accelerated downward with acceleration \'a\'. A man in the lift throws a ball upward with acceleration a0(a0< a). Then, acceleration of ball observed byobserver, which is on Earth, is
  • (a + aupward
  • (a –aupward
  • (a + adownward
  • (a –adownward
If in a stationary lift, a man is standing with a bucket full of water, having a hole at its bottom. The rate of flow of water through this hole is R0. If the lift starts to move up and down with same acceleration and then that rates of flow of water are Ru and Rd, then
  • R0 > Ru >Rd
  • Ru > R0 >Rd
  • Rd> R0 > Ru
  • Ru >Rd > R0
A gun fires N bullets per second, each of mass m with velocity v. The force exerted by the bullets on the gun is

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A man is standing at the centre of frictionless pond of ice. How can he get himself to the shore?
  • By throwing his shift in vertically upward direction
  • By spitting horizontally
  • He will wait for the ice to melt in pond
  • Unable to get at the shore
A student attempts to pull himself up by tugging on hishair. He will not succeed
  • As the force exerted is small
  • The frictional force while gripping, is small
  • Newton's law of inertia is not applicable to living beings
  • As the force applied is internal to the system
A body floats in a liquid contained in a beaker. If the whole system as shown in figure falls freely under gravity, then the upthrust on the body due to liquid is
Physics-Laws of Motion-77251.png
  • Zero
  • Equal to the weight of liquid displaced
  • Equal to the weight of the body in air
  • None of the above
A bird weighs 2 kg and is inside a closed cage of 1 kg. If it starts flying, then what is the weight of the bird and cage assembly?
  • 1.5 kg
  • 2.5 kg
  • 3 kg
  • 4 kg
A man is standing on a balance and his weight is measured. If he takes a step in the left side, thenweight
  • Will decrease
  • Will increase
  • Remains same
  • First decreases then increases
A cold soft drink is kept on the balance. When the cap is open, then the weight
  • Increases
  • Decreases
  • First increases then decreases
  • Remains same
A bird is sitting in a large closed cage which is placed on a spring balance. It records a weight of 25 N. The bird (mass m = 0.5 kg) flies upward in the cage with an acceleration of 2 m/s2. The spring balance will nowrecord a weight of
  • 24 N
  • 25 N
  • 26 N
  • 27 N
A light spring balance hangs from the hook of the other light spring balance and a block of mass M kg hangs from the former one. Then the true statement about thescale reading is
  • Both the scales read M/2 kg each
  • Both the scales read M kg each
  • The scale of the lower one reads M kg and of the upper one zero
  • The reading of the two scales can be anything but the sum of the reading will be M kg
The tension in the spring is
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  • Zero
  • 2.5 N
  • 5 N
  • 10 N
0:0:1


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