Friction Questions and Answers

444 k A force is applied on the block in downward direction which increases very slowly When this force becomes F the spring breaks What should be the value of a minimum constant force F applied in the given case such that the spring breaks SolveLancer Test a m d F mg 2 b F mg C F 1 mg F

stopped 12 ed a area of surfac normal reaction 3 c direction of applied force 1x x x d none of the above 206 The static friction is to he 205 The s 214 If in of p the b of t alon a equal to the dynamic friction a b always less than the dynamic friction L C c always greater than the dynamic friction 215 A sometimes greater and sometimes equal to for friction of to 207 Which of the following statements is true More force is required to start a motion than to it against friction V 0 10 1 10

219 A box is placed on an inclined plane and has to be pushed down The angle of inclination is a equal to angle of friction b more than angle of friction c equal to angle of repose d greater than angle of repose 220 An object is placed on the surface of a smooth inclined plane of inclination 0 It takes time t to reach the bottom If the same object is allowed to slide down a rough inclined plane of inclination 0 it takes time nt to reach the bottom TI coofficient of

62 A constant force F has been applied upon the plank of mass M Upon plank a thin circular wheel of mass m and radius R has been placed There is no slipping between plank and wheel Wheel 0 The friction force upon wheel will be 2m 1 2M m m F F m 0 18 P M 2 4 F m 2M m 2m M 2m F

A body of mass 1 kg rests on a horizontal floor with which it has a coefficient of static 1 13 It is desired to make the body move by applying the minimum possible force 3 friction FN The value of F will be Take g 10 ms 2 Round off to the Nearest Integer

Two blocks A and B of masses m 1 kg and mB 3 kgare kept on the table as shown in figure The coefficient of friction between A and B is 0 2 and between B and the surface of the table is also 0 2 The maximum force F that can be applied on B horizontally so that the block A does not slide over the block Bis Take g 10 m s 2019 Main 10 April II A B F

c 2n 230 A lift is moving upwards with a uniform velocity vi a block of mass m is lying The frictional force offered by the block when coefficient of friction is u will be a zero e umg b mg d 2 mg lift T

A mass m on the surface of the Earth is shifted to a target equal to the radius of the Earth If R is the radius and M is the mass of the Earth then work done in this process is A B mgR 2 Correct Answer mgR 2 mgR maR

Q 20 Moderate 0 75 4 1 00 23 O 000 A bullet of mass 0 02 kg travelling horizontally with velocity 250 ms strikes a block of wood of mass 0 23 kg which rests on a rough horizontal surface After the impact the block and bullet move together and come to rest after travelling a distance of 40m The coefficient of sliding friction of the rough surface is q 9 8ms

33 A time varying force is applied on a block placed over a rough surface as shown in figure Let 0 be the angle between net contact force on the block and the normal reaction then with time 0 will F 2t Rough a remain constant b first increase to a maximum value say Omax and then becomes constant in a value less then max c first decrease to a minimum value say 0min and then becomes constant in a value more then min d None of the above 34 In the figure two blocks are given velocities as shown

39 A force F t 13 block A as shown in figure The force is applied at t 0 seconds when the system was at rest and string is just straight without tension Which of the following graphs gives the friction force between B and horizontal surface as a function of time t a c F F b d M F F Rough M F t

Determine the work done by the frictional force in drawing a circle of radius 2R by a pen of negligible mass with a normal pressing force N Consider coefficient of friction as U 4 R N 2 R N 4 R N

34 In the figure two blocks are given velocities as shown The lower block is very long Find velocities of both the blocks when relative motion between them is ceased 2 m s m 0 5 1 kg 2 kg Smooth a 2 m s towards right b 1 m s towards left c 2 m s towards left 7 m s

A 4 kg box is pulled along a horizontal surface uk 0 23 by a light and inelastic rope over a light and frictionless pulley by a 3 kg hanging mass a Find the acceleration of the box and the tension in the rope b Compute the acceleration of the box and the tension in the rope if the 3 kg mass is placed on a smooth inclined plane with an angle of inclination of 57

For a system to be in equilibrium the torques acting on it must balance This is true only if the torques are taken about The centre of the system The centre of mass of the system Any point on the system Any point on the system or outside it

121 A body of mass m was slowly hauled up the hill Fig 1 29 by a force F which at each point was directed along a tangent to the trajectory Find the work performed by this force if the height of the hill is h the length of its base 1 and the coefficient of friction k buy 122 A disc of mass m 50 g slides with the zero initial velocity down an inclined plane set at an F Fig 1 29

d pers 4 A rod of length 4 m is suspended from two wires as shown in figure One of them is made of steel and other of copper of cross sectional area 10 2m2 and 4 x 10 2 m Find distance x if equal stress is 2 x 1011 N m experienced by both the wires Y and Y Copper 1 1 x 10 1 N m Steel 1 2 m Steel xx W Copper 2 3 5 m

In the figure shown force F at applied on the block m Here a is a constant and t is the time Find the acceleration of the blocks 0 m m

In the given figure the angle of inclination of the inclined plane is 30 Find the horizontal velocity Vo so that the particle hits the inclined plane perpendicularly A V 2gH V 5 C V 1 gH 5 B V D V 2gH V 7 gH 7 90 Vo H 30 90

a d 0 48 m inclined rough surfaces of height h each The angles of inclination of the two planes are 30 and 60 respectively All other factors e g coefficient of friction mass of block etc are same in both the cases Let K and K be the kinetic energies of the particle at the bottom of the in the two cases Then plane a K K c K K b K K d Data insufficient

A ball of mass m is suspended from the ceiling with the help of an elastic cord An additional downward force applied on the ball if increased gradually to a value Fo the cord would break What should be the additional minimum constant force that will break the cord a F F c F F mg b F F mg d F F mg

80 kg 20 m s 14 A cart is moving to the right with a constant speed of 20 m s A box of mass 80 kg moves with the cart without slipping The coefficient of static friction between the box and cart is 0 30 and the coefficient of kinetic friction between the box and cart is 0 15 What are the magnitude and direction of the frictional force acting on the box as it moves with the cart A Zero B 120 N to the right C 120 N to the left D 240 N to the right E 240 N to the left

A block of mass 60 kg slides over a horizontal distance of 0 9 m If the coefficient of friction between their surface is 0 15 then work done against friction is 79 4 j Correct Answer Your Answer

The circuit shown in the figure consists of a battery of emf E resistances R and R2 inductance L and a two way switch ABC First A is connected to B for a long time and then A is connected to C The total heat produced in R is A L C E R LE2 2R 2 B D LE2 2R 2 LE 2 R R 46 E R mooo L

A block of mass m rests on a horizontal table executing SHM along horizontal with amplitude A when block just starts to slip then the perioc u coefficient of friction is 1 2 3 T A g A uq 2 2 4 2 A g 2A ug

14 In case i wedge B is stationary and block A starts sliding when the angle of plane is greater than a certain value 0 while in case ii wedge B is moving upwards with an acceleration ao and the block A starts sliding when the angle of plane is greater than a Coefficient of friction between A and B in both the cases is same Then Tao a 0 a c 0 a A 1 B A b 0 a tane d tana ii B g ao

The Electricity developed on objects when they are rubbed with each other is called a Frictional Electricity b Electrified c Polarity d Viterons

2 A series LCR circuit consists of an inducto capacitor C and a resistor R connected across a source of emf sin oot When L current in the circuit is and if angular frequency of the source is changed to wo the current in the circuit 10 2 becomes then the value of L 1 R 3 C R mw L sin cof 2 3 R 1 C 1 w C the is

84 Two bodies of masses m and 4m are attached to a light string as shown in Fig 8 262 A body of mass m hanging from string is executing oscillations with angular amplitude 60 while other body is at rest on a horizontal surface The minimum coefficient of friction between mass 4m and the horizontal surface is here pulley is light and smooth a 1 b 3 4 m Fig 8 262 1

A body of mass m falls from rest at a height y If the drag resisting force of air is assumed to be proportional to the instantaneous velocity v of the body Use k as the proportionality constant and take y 0 at ground level 1 Find the height of the body y as a function of its velocity v 2 Find the height of the body y as a function of time t 3 Assuming that g 9 81 m s m 1 kg y height of the body 20 seconds after it starts 2000 m and k 0 01 calculate the falling

The system of two blocks is at rest as shown in the figure A variable horizontal force is applied on the upper block The coefficient of friction for both the contacts is u Choose the correct option s 4 L Net horizontal force on the lower block is always zero m 2m F Ground mg v When acceleration of the upper block is 2 g net force on the lower block by the ground in When acceleration of the upper block is 2 g acceleration of the lower block is zero Unless the upper block moves no frictional force exists between the ground and the lower block 9

2 27 A and B are two points 28 cm apart on a inclined plane and the difference in level between them is 15 cm A force of 300 g wt applied parallel to the plane is just sufficient to drag a log of 0 36 kg up the plane Calculate 1 the force of friction 2 the normal reaction and 3

J A m is kept over another block of mass M and the system rests on a horizontal surface figure 8 E1 A constant horizontal force F acting on the lower block produces an acceleration F in the 2 m M system the two blocks always move together a Find the coefficient of kinetic friction between the bigger block and the horizontal surface b Find the frictional force acting on the smaller block c Find the work done by the force of friction on the smaller block by the bigger block during a displacement d of the system M 3 Figure 8 E1 F

ng figure shows two blocks A and B pushed against the wall with a force F The wall is smooth but the surfaces in contact of A and B are rough Which of the following is true for the system of blocks to be at rest against the wall Wall A B 1 F should be be more than the weight of A and B 2 F should be equal to the weight of A and E 3 F should be less than the weight of A and 1 1

A block of mass 5 and ii pulled in case B by a force F 20 N making an angle of 30 with the horizontal as shown in the figures The coefficient of friction between the block the floor is between the u 02 The difference accelerations of the block in case B and case A will be Take g 10 ms 2 JEE Main 2019 12 April Shift II F 20 N 30 F 20 N 30 A B a 0 4 ms 2 b 3 2 ms 2 c 0 8 ms d 0 ms 2 Fro c

09 A block slides with constant velocity on a plane inclined at an angle 0 The same block is pushed up the plane with an initial velocity vo The distance covered by the block before coming to rest is 1 3 v 2g sin 0 vsin 0 2g 2 4 v 0 4g sin 0 v sin 0 4g

A drive train has a driving gear with 12 teeth and a radius of 1 inch and a driven gear with 36 teeth and a radius of 3 inches In this case a b 3 the torque is multiplied by 3 and the speed is reduced by 1 3 the torque is reduced by 1 3 and the speed is multiplied by 3 both the torque and the speed are reduced by 1 3 both the torque and the speed are multiplied by 3

07 The force required to just move a body up an inclined plane is double the force required to just prevent the body from sliding down the plane The coefficient of friction is u The inclination 0 of the plane is 1 tan 2 tan 2 3 tan 2 4 tan 3

The friction coefficient between a road and the tyre of a vehicle is 4 3 Find the maximum incline the road may have so that once hard brakes are applied and the wheel starts skidding the vehicle going down at a speed of 36 km hr is stopped within 5 m

0 The angle between the resultant contact force and the normal force exerted by a body on the other is called the angle of friction Show that if be the angle of friction and u the coefficient of static friction tan 1

21 A block of mass m is kept on a horizontal ruler The friction coefficient between the ruler and the block is u The ruler is fixed at one end and the block is at a distance L from the fixed end The ruler is rotated about the fixed end in the horizontal plane through the fixed end a What can the maximum angular speed be for which the block does not slip b If the angular speed of the ruler is uniformly increased from zero at an angular acceleration a at what angular speed will the block slip

packet is dropped from rest onto a conveyor belt which is unning with a velocity v If the coefficient of kinetic friction between the package and belt is u find the a maximum Histance of sliding of the packet relative to i the ground ii the belt and b time of relative sliding of the packet

5 A bullet of mass 0 05 kg moving with a speed 5 of 80 m s enters a wooden block and is stopped after a distance of 0 40 m The average resistive force exerted by the block on the bullet is 1 300 N 2 20 N 3 400 N 4 40 N A man of mass 40kg is holding a vertical pole The coefficient of static friction between his hands and the pole is 0 4 If he is able to climb up the pole What is the minimum force with which he should press the pole with his hands g 10 m s 1 1000 N 3 160 N 2 400 N 4 500 N 6

A person with a mass m stands in contact against a rough wall of cylindrical drum rotor of radius R without floor The rotor is rotating about its axis with angular speed w rad s What is minimum coefficient of friction required such that person does not slip down R gR w 2gR w g Rw Rw 2 a

In the arrangement shown in figure m 4 0 kg and m 1 0 kg The system is released from rest and block B is found to have a speed 0 3 m s after it has descended through a distance of 1 m Find the coefficient of friction between the block A and the table Neglect friction elsewhere Take g 10 m s A B X 4

A mouse with mass mm 200 g sits on a wedge shaped block with mass m 850 g and inclination angle 0 40 The block rests on a spring scale as seen in the diagram below The top of the block is a frictionless surface and the mouse slides down the block freely Friction between the block and the spring scale is large enough such that the block does not slip on the scale a Draw a free body diagram for both mm and m Clearly label all relevant forces as well as your coordinate system choice Indicate if any forces make Newton s 3rd Law pairs b Write out Newton s Second Law for each relevant direction in your coor dinate system c What does the spring scale read in Newtons as the mouse slides down the block

A block slides with constant velocity on a plane inclined at an angle 0 The same block is pushed up the plane with an initial velocity v The distance covered by the block before coming to rest is 1 vo 2g sin 0 2 v 4g sin 0 3 v sin 0 2g 4 v sin 0 4g

A block of mass m is placed on the top of bigger wedge M All the surfaces are frictionless The system is released from rest Find the distance moved by smaller block w r t triangular wedge when bigger wedge travels distance X on plane surface m M 30

A block having mass m is placed over an inclined wedge of same mass and o inclination 45 to the horizontal to the co efficient of friction between all surfaces o contact is same and equal to Now the system is free to move then m A For 1 block over incline will move but wedge will not B For 0 3 1 block will move but wedge will not C For 0 15 both will move D It is not possible to move wedge without block over wedge

A body is executing SHM with amplitude of xo Its angular frequency is w At some position on its path its potential energy is equal to kinetic energy The velocity of particle at that instant is Assume potential energy is zero at mean position 30x0 NIECO 550 X0 2 Xn