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Solved examples
Question 1 Force exerted on a body changes it's
(a) Direction of motion
(b) Momentum
(c) Kinetic energy
(d) All the above
Question 2 there are two statements
A Rate of change of momentum correspondes to force
B Rate of change of momentum corresponds to Kinetic Energy
Which of the following is correct
(a) A only
(b) B only
(c) Both A and B are correct
(d) Both A and B are wrong
Question 3 A truck and car are moving on a plane road with same kinetic Energy. They are brought to rest by application of brakes which provide equal retarding forces. Which of the following statements is true.
(a) Distance travelled by truck is shorter then car before comming to rest
(b) Distance travelled by car is shorter then truck before comming to rest
(c) Distance travelled depends on individual velocity of both the vehicles
(d) Both will travel same distance before comming to rest
Question 4 A block A of mass m1 is released from top of smooth inclined plane and it slides down the plane. Another block of mass m2 such that m2 > m1is dropped from the same point and falls vertically downwards. Which one of the following statements will be true if the friction offered by air is negligible?
(a) Both blocks will reach ground at same time
(b) Both blocks will reach ground with the same speed
(c) speed of both the blocks when they reach ground will depend on their masses
(d) Block A reaches ground brfore block B
Question 5 Which of the following observer is/are non interial
a.A child revolving in the merry ground
b. A driver in a train moving with constant velocity v
c. A passenger in a bus which is slowing down to a stop
d None of these
Question 6 there are two statements
A Newtons first law in valid from the pilot in an aircraft which is taking off
B Newtons first law in valid from the observer in a train moving with constant velocity
Which of the following is correct
(a) A only
(b) B only
(c) Both A and B are correct
(d) Both A and B are wrong
Question 7A IITJEE text book of mass M rests flat on a horizontal table of mass m placed on the ground.Let RX->Y be the constant force exerted by the body x on body Y.According to Newton third law,which of the following is an action-reaction pair of forces?
a. (M+m)g and Rtable->book
b. Rground->table and mg+Rbook->table
c. Rground->table and Rtable->ground
d Mg and Rtable->book
Question 8 Choose the correct alternative
a. The acceleration of a moving particle is always in the direction of its velocity
b. Velocity and acceleraion vectors of a moving particle may have any angle between 0 and 360 between them
c.Velocity and acceleraion vectors of a moving particle may have any angle between 0 and 180 between them
d. If the acceleration vector is always perpendicular to the velocity vector of a moving particle,the velocity vector does not change
Question 9 A block of mAss M is moving with a velocity v on straight surface.What is the shortest distance and shortest time in which the block can be stopped if μ is coefficent of friction
a.v2/2μg,v/μg
b. v2/μg,v/μg
c.v2/2Mg,v/μg
d none of the above
Question 10A horizontal force of F N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is μ. The weight of the block is
a.μF
b. F(1+μ)
c. F/μ
d none of these
Question 11.A body is sliding down a rough inclined plane of angle of inclination θ for which coefficent of friction varies with distance y as μ(y)=Ky where K is constant.Here y is the distance moved by the body down the plane.The net force on the body is zero at A.Find the value of constant K
a. tanθ/A
b. Acotθ
c. cottanθ/A
d. Atantanθ
Question 12 there are two statements
A Newtons first law in valid from the pilot in an aircraft which is taking off
B Newtons first law in valid from the observer in a train moving with constant velocity
Which of the following is correct
(a) A only
(b) B only
(c) Both A and B are correct
(d) Both A and B are wrong
Question 13.A body of mass 5 kg starts from the origin with an intial velocity u=30i+40j m/sec.If the constant force acts on the body F=-(i+5j) N.The time in which y component of the velocity becomes zero is
a. 5 sec
b. 80 sec
c. 20 sec
d. 40 sec
Question 14.A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle.The motion of the particle takes place in a plane.it follows that
a. velocity is constant
b. accelerattion is constant
c. KE is constant
d. Particle moves in a circular path
Question 15A small mass m is suspended from one end of a vertical string. and then whirled in a horizontal circle at a constant speed v.
Which of the followings is true
a.The strings stays vertical
b.The string becomes inclined to the vertical.
c.There is no force on mass m except its weight
d.The angle of inclination of the string does not depend on the v
e.The centripetal force on m is mg
Question 16.A IITJEE text book of mass M rests flat on a horizontal table of mass m placed on the ground.Let RX->Y be the constant force exerted by the body x on body Y.Which of the following is true for the forces Rground->table and Rtable->ground
a. It is action and reaction pair
b. have equal magnitude
c. Opposite direction
d.have resultant zero
Question 17.The tension in cable supporting an elevator is equal to th weight of the elevetor.The elevator may be
a. going up with incresing speed
b. going down with increasing speed
c. going up with uniform speed
d. going down with uniform speed.
Question 18 A refrence frame attached to the earth
a.is an inertial frame by defination
b.cannot be inertial frame as earth is revolving around the sun
c.is an intertial frame because Newton's law are applicable in this frame
d.cannot be intertial frame because earth is rotating about its own axis
Question 19By means of rope ,a body of weight W is moved vertically upward with constant acceleration a .Find the tensile force in the rope
a. W(1+a/g)
b W(1-a/g)
c W
d. none of the above
Question 20A given object takes n times as much times to slide down a 45 rough incline as its takes to slide down a perfectly smooth 45 incline.The coefficent f kinectic friction between the objects and incline is gievn by.
a. 1/(1-n2)
b.1-1/n2
c. √1/(1-n2)
d. √(1-1/n2)
Question 21A uniform chain of length L is lying on the horizontal surface of a table.If the coefficent of friction between the chain and the table top is μ. what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on table.?
a.L/(1+μ)
b. μL/(1+μ)
c. L/(1-μ)
d. μL/(1-μ)
Question 22The coefficent of static and kinectic friction between a body and the surface are .75 and .50 respectively.A force is applied to the body to make it just slide with a constant acceleration which is
a. g/4
b g/2
c. 3g/4
d g
Question 23 A block of mAss M is moving with a velocity v on straight surface.What is the shortest distance and shortest time in which the block can be stopped if μ is coefficent of friction
a.v2/2μg,v/μg
b. v2/μg,v/μg
c.v2/2Mg,v/μg
d none of the above
Question 24A horizontal force of F N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is μ. The weight of the block is
a.μF
b. F(1+μ)
c. F/μ
d none of these
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