Friction Questions and Answers

1 0 02 2 0 03 A block rests on a rough inclined plane making an angle of 30 with the horizontal The coefficient of static friction between the block and the plane is 0 8 If the frictional force on the block is 10 N the mass of the block in kg is take g 10 m s AIEEE 2004 2 0 2 4 0 3 1 6 4 2 5 AIEEE 2005 longed at rest on a 45 incline and then slides a distance d The time taken to slide is n times incline The coefficient of friction is

3 936 ms 2 2 936 ms 3 ms A gramophone record is revolving with an angular velocity o A coin is placed at a distance r from the of the record The static coefficient of friction is u The coin will revolve with the record if AIPMT 2 1 r go ug 3 TS H 4 r2 r ug w 2 ug Ona leyel circular track of radius R If u represents the static friction between in circular motion is given by AIPMT Main 20

n The upper half of an incline plane with inclination is perfectly smooth while the lower half is rough A body starting from rest at the top will again come to rest at the the bottom if the coefficient of friction for the lower AIEEE 2005 half is given by 1 2 tan 2 tan 3 2 sin 4 2 cos ving on a straight road with a speed of 100 m s The distance at which car can be stopped AIEEE 2005

42 0 2 4 0 3 1 6 A smooth block is released at rest on a 45 incline and then slides a distance d The time taken to slide is n times as much to slide on rough incline than on a smooth incline The coefficient of friction is AIEEE 2005 1 1 2 2 n 2 H 3 1 4 H n on is perfectly smooth while the lower half is rough A body 2

A block W is held against a vertical wall by applying a horizontal force F The minimum value of F needed to hold the block is if u 1 1 Less than W 3 Greater than W 2 Equal to W 4 Data is in insufficient rough horizontal plane is acted upon by a horizontal force P and another force

A plank with a box on it at one end is gradually raised about the other end As the angle of inclination with the horizontal reaches 30 the box starts to slip and slides 4 0 m down the plank in 4 0 s The coefficients of static and kinetic friction between the box and the plank will be respectively NEET 2015 1 0 5 and 0 6 2 0 4 and 0 3 mg 3 0 6 and 0 6 4 0 6 and 0 5

A block A of mass m rests on a horizontal table A light string connected to it passes over a frictionles pully at the edge of table and from its other end another block B of mas m is suspended The coefficient of kinetic friction between the block A is sliding on the table the tension in the strng is NEET 2015 m m 1 g m m 1 2 m m 1 g m m 3 m m g m m 4 m um g m m

A block of mass m is kept on disc at rest Disc starts rotating with constant angular acceleration a Friction between block disc in sufficient to prevent slipping Which of the following is are correct 450 In inertial frame net force on the block is equal to friction force Normal on block increases with time Friction force will be towards centre Friction force on the block is not constant r

The figure below shows an initially stationary block of mass m on a floor A force of magnitude F 0 530mg is then applied at upward angle 8 24 a What is the magnitude of the acceleration of the block across the floor if the friction coefficients are us 0 595 and Uk m s 0 510 b What is the magnitude of the acceleration of the block across the floor if the friction coefficients are us 0 395 and 0 305 m s

A block of mass m is released from the top of a 23 wedge of mass M as shown in figure All the surface are smooth Let N be the normal reaction between the ground and the wedge then inga og X M mg A N M m g B N m M g C N M m a 0

2 A block of mass 0 2 kg is held against by a wall by applying a horizontal force of 5 N on the block The coefficient of friction between the wall and block is 0 5 Find the magnitude in Newton of the frictional force acting on the block Take g 10 m s a 2 IIT 1994 b 4 c 8 d 0

In the given string pulley arrangement all the pulleys and strings are massless and smooth The acceleration of block will be ZUL 901 1 g 4 3 g 2 D Halle GE m 2 4 g GOBROL 2 g 8 from C

Q5 In the arrangement shown mass of pulley P is m and pulley Q is massless Both the pulleys are frictionless There is friction between m and ground whereas surface between 2m and inclined plane is smooth If the system is in equilibrium force applied by clamp on pulley P is Options mg 2 30 mg 3i 57 mg 31 57 2 3i 37 mg 31 33 m

1 A box with a mass of 4 00 kg sits on top of a box with a mass of 6 00 kg The coefficient of kinetic friction between the boxes is 0 250 The coefficient of kinetic friction between the bottom box and the table is 0 500 Each box is attached to a string and they are pulled in opposite directions The string attached to the bottom box has a tension of 60 0 N and the string attached to the top box is pulled so the top box stays stationary a What is the acceleration of the bottom box before it slides out from under the top box b What is the tension holding the top box in place

Two blocks with masses M and M are connected by a massless string that passes over a massless pulley as shown M has a mass of 2 25 kg and is on an incline of 45 5 with coefficient of kinetic friction 0 205 M has a mass of 6 95 kg and is on an incline of 02 34 5 with coefficient of kinetic friction 0 105 The two block system is in motion with the block of mass M sliding down the ramp Find the magnitude a2 of the acceleration of M down the incline a m s M 0 M 12 M Figure is not to scal

the bigge A Sh wedge of mass M slides or wedge initially resting on the smooth horizonta ground as shown in the figure The mass of the bigger wedge is 6M When the smaller wedge reaches the base of the bigger wedge the distance move by the bigger wedge is the fi JEE Fou 1 L M 21 6M 4L 2 4L 5 31

3 SK 4 6k 44 In the arrangement shown all surfaces are frictionless The rod R is constrained to move vertically The vertica acceleration of R is a and the horizontal acceleration of the wedge W is a The ratio is equal to 1 sina 3 tana W 2 cosa 8

09 A massive bead is threaded on a light rod that is pivoted to a fixed point O at one end Initially the rod is held in a horizontal position and the bead is at a distance from the pivoted end When the rod is released it rotates in a vertical plane and the bead slides down the rod due to gravity Which of the following statements best suits for dependence of the angle 9 that the rod makes with the horizontal on time t A If coefficient of friction between the rod and the bead is negligible 0 tan B If coefficient of friction between the rod and the bead is finite 0 tangt 2 C If coefficient of friction between the rod and the bead is finite 0 tan D None of the above statements is true 2 gt 21

A block of mass m lying on a rough horizontal surface of friction coefficient u is pulled by a force Fas shown the limiting friction between the block and surface will be m AF 30 G

9 A block of mass 5 kg is placed over a rough horizontal surface with coefficient of friction 0 1 There is a horizontal force of 13 N is acting on it towards right and another horizontal force F is acting on it towards left Taking g 10 m s the range of F over which block does not slip is 1 8 F 18 N 2 0 F 18 N 3 Any value less than 18 N 4 Any value above 18 N

5 Three one over the other as shown in figure Find the minimum force needed to cause the motion in any part of the system Coefficient of friction is written for every surface on side C 0 4 0 3 0 1 B A 4 kg 6 kg 10 kg F

curves drawn between frictional 7 force f and applied force F for 2 bodies on ground Then correct statement is f 40 N A 20 N B F 1 0 0 2 Coefficient of static friction may be more for B 3 Coefficient of kinetic friction is same as coefficient of static friction for both A B 4 Coefficient of static friction

is pulling a wagon on a rough surface with constant velocity Rough Surface A The net force on the system wagon is in forward direction B Nature of friction on both wagon and horse is same C The energy is lost due to friction acting on the horse D The friction supplies energy to the horse The total number of incorrect statements is 1 0 3 3 Consider three 2 2 4 4

Total number of correct statements are A Tension may be impulsive force B Gravitational force may be impulsive force C Spring force can never be impulsive force D Frictional force can never be impulsive 1 1 2 2 3 3 4 Zero

13 4 A D C B Surface between blocks is sufficiently rough and surface between block and ground is smooth Assume starting from rest Which of the following is incorrect 10N 2kg 4kg A Block C 10N 16N Case T 2kg 1 2 kg A 2 2 kg B 3 4 kg A 4 4 kg B If v P at rt Then 4kg B Direction of motion 16N Direction friction

10 A body kept on a smooth inclined plane of inclination 1 in x will remain stationary relative to the inclined plane if the plane is given a horizontal acceleration equal to B D A x 1g gx C 1 x 1 X X g

The value of acceleration and friction force in the given diagram is Ms 0 4 MK 0 3 53 F 500N 12 kg 1 4 m s upward 120 N 2 4 m s downward 120 N 3 5 m s upward 36 N 4 5 m s upward 120 N

A particle is released from rest from a top of incline plane of angle 37 Top rd is smooth and bottom 3rd is rough If again come to rest at bottom Friction co efficient is a 3 8 b 3 16 c 3 4 d 9 8

2 points possible graded A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 807 N on hi The mass of the losing player plus equipment is 89 kg and he is accelerating at 1 4000000000000001 m s backward a What is the force of friction between the losing player s feet and the grass b What force does the winning player exert on the ground to move forward if his mass plus equipment is 106 kg

Draw an orbital energy level diagram like those in Fig 23 23 showing the configuration of the d electrons on the metal ion in each of the following complexes a Co NH3 6 b NiCl4 tetrahedral c Fe H O d Fe CN 6

What is the minimum force that needs to be applied on a body of mass 100 g kept on a horizontal surface to set the body in motion Given coefficient of friction between the surface and the body is 0 4 and the force acts parallel to the surface 39200 dyn

A 30 kg block rests on a rough horizontal surface A force of 200 N is applied on the block The block acquires a speed of 4 m s starting from rest in 2 s What is the value of coefficient of friction Question Type Single Correct Type 1 0 33 2 0 17 3 0 47

1 e force 5t N is applied on a block as shown in figure where t is time in second If coefficient of friction force between block and surface is then find the time in sec at which block just starts to move 3 F 5t m 6kg

In the figure shown ground smooth whereas surface between 3 kg block and 2 kg block is rough A force of magnitude 10 N is applied on 3kg block horizontally If net work done by friction on the system on 3 kg and 2 k blocks in any time frame is zero then coefficient of friction between 3 kg and 2 kg can be 0 1 03 04 2kg 3kg Rough 10N Smooth

A block of mass 2 kg initially is at rest on a rough surface having coefficient of friction p 0 5 A force 20N is applied as shown in figure then which of the following is are CORRECT 20N 0 Acceleration of block is 6m s Work done by applied force F when block has moved by 2m is 323 Work done by kinetic friction when block has moved by 2m is 8 J Magnitude of normal contact force applied by block on the ground is BN 2kg F 0 5

Three blocks A B and C are placed on a rough horizontal surface Friction coefficient between blocks and surface is 0 6 Acceleration of the block C given situation is g 10 m s 4 kg A 6 kg B 3 5 m s O 0 5 m s O 4 5 m s O Zero C 5 5 kg

x An inclined plane is bent in such a way that the vertical cross section is given by y where y is in vertical and x in horizontal direction If the upper surface of this curved plane is rough with coefficient of friction 0 5 the 4 cm maximum height in cm at which a stationary block will not slip downward is orrect Answer 25 00 swer 8 ect

In adjacent diagram the ratio of mass m and m m m so that they remain at rest given all surfaces are smooth and inclined faces are fixed is 16 X Value of x is wwwwwww m 37 m 53

PARAGRAPH Relation b w friction and applied force for a block of mass 2 kg on rough horizontal surface is given by below graph 27 28 fL 20 NL fk 18 N Friction O Applied force Find the value of frictional force if applied force on block is 10 N A 20 N B 18 N C 10 N D O Find the value of acceleration of block if applied force is 30 N A 8 m s B 5 m s C 6 m s R 4 m s

11 A ladder of mass M and length L is supported in equilibrium against a smooth vertical wall and a rough horizontal surface If 0 be the angle of inclination of the rod with the horizontal then normal reaction of the wall on the ladder is 30 Tub 1 Mg 2 3 4 Mg 2 tane Mgcote 3 Mg 20058 elpoe 0 rough smooth 200

An insect crawls up a hemispherical surface very slowly The coefficient of friction between the insect and the surface is 1 3 If the line joining the center of the hemispherical surface to the insect makes an angle a with the vertical the maximum possible value of a is given by cot a n Find n

Static friction fs is a constraint force because it prevents relative sliding between contacting surfaces It acts tangentially to the surfaces in contact Hence we call it tangential contact force It is a macroscopic effect of intermolecular forces between the molecules of the surface in contact Static friction basically is an interlocking of the microscopic surface irregularities projection When the surfaces tend to slide fs comes into play The tendency of relative sliding is characterised by a relative acceleration in the absence of friction We can find the relative acceleration a12 and a21 of each surface by as usual process by drawing FBD and writing force equations excluding frictional forces between the surfaces under consideration If the surface 1 has acceleration a12 relative to surface 2 static friction s acts on surface 1 in opposite direction of 12 Similarly 52 acts on surface 2 opposite to 21 Thus static friction opposes the tendency of relative sliding for 1 7

Two short magnets of equal dipote moments M are fastened perpendicularly at their centres as given in the figure The magnitude of the magnetic field at a distance d from the centre on the bisector of the right angle is Ho M a Ho 4n d NC c H 2 2M 4 d 9 P N S b Ho S 2 M 4 d AIIMS 2016 d Ho 2M 4 d

Two blocks of mass M 6 kg and m H 3 kg are placed as shown in the figure Coefficient of friction between M and m is 0 5 Coefficient of friction between M and the surface is 0 4 The maximum horizontal force that can be applied to the mass M so that they move without separation is g 10 ms 1 41 N 2 61 N 3 81 N 4 101 N ALLEN m 3 kg M 6 kg M 6 3 fan anat geen ant 0 5 fm 3 Tu for at 0 4 TERIMA SEI CHIRI SI FET g 10 f m 3 kg M 6 kg 1 412 2 61 3 81 55 4 101

In the figure 8 kg and 6 kg are hanging stationary from a rough pulley and are about to move They are stationary due to roughness of the pulley Which of the following statement s is are correct I The force of friction on the rope is 20 N II The force of friction on the rope is 30 N a Only I b Only II c Neither I nor II d None of these O 8 kg 6 kg

649001 Friction Calculate the magnitude of the deceleration of a snow boarder going up a 4 67 slope assuming the coefficient of friction for waxed wood on wet snow 0 14 40 Please enter a numerical answer below Accepted formats are numbers or e based scientific notation e g 0 23 2 1e6 5 23e 8

m m 3 Now a new block with mass m 16 2 kg is attached to the first block The new block is made of a different material and has a greater coefficient of static friction What minimum value for the coefficient of static friction is needed between the new block and the plane to keep the system from accelerating

162 A 8 kg block A is placed on 2 kg block B which rests on a table Coefficient of friction between A and B is 0 5 and between B and table is 0 2 A 60 N horizontal force is applied on the block A then the friction force between the blocks A and B is 1 Zero 3 28 N 2 2 5 N 4 40 N

An object of mass M is gently placed on a horizontal conveyor belt which is moving with uniform velocity v as shown in the figure The coefficient of static friction is u the coefficient of kinetic friction is and the acceleration of gravity is g Initially the object slips for a while but finally moves without slipping together with the belt How far the conveyor belt moves while the object is slipping A g B 2 g C g poooo D 2 g

A block of mass m is kept on a wedge of mass M The block and wedge both remain at rest rough The force of friction acting on the wedge due to the block kept on the wedge is A mg sin e B mg cos 0 C mg The net contact force between the wedge and the block is A mg sin e B mg cos 0 C mg M C rough D data insufficient D None of these