Friction Questions and Answers

a 10 3 N b 23 8 N c A block of mass M is held against a rough vertical wall by pressing it with a finger If the coefficient of friction between the block and the wall is and the acceleration due to gravity is g what is the minimum force required to be applied by the finger to hold the block against the wall a Mg b Mg c Mg d 2 Mg A trolley of mass 20 kg is attached to a block of mass A The Take a 4 b 6 c 8 d 10 71 A cyc a re

3 a b Three charges Q each are kept at corners of an equilateral triangle and another charge q is kept at its centre as shown The ratio of q and Q so that system is in equilibrium Q 1 1 2 3 1 Q 2 1 2 3 C 5

m 20 kg m Find the acceleration of m and m for the following figures a and b When 6 m m 30kg F 160 N F 30 kg m is on smooth surface Surface between m and m has 175 N 98 160 160 F 32 0 98 418 m m F 160 N F 0 5 and 0 3 MAY

18 Figure given along side shows a block pressed against a rough vertical wall with a force F as shown in side view Column I shows angle at which force F is applied and Column II gives information about corresponding friction match them Column I F m F 100N m 7 5kg 0 1 Column II p friction by wall on block is upwards q friction by wall on block is downwards r friction by wall on block is static s friction by wall on block is kinetic A 0 37 B 0 45 C 0 53 D 0 0 A a p s b p r c q s d p r B ar s b p s c qr dp s C a p s b p c r d p s D a p s b p r c q r d p s

A horizontal force is applied on a wedge which is kept on a horizontal surface as shown in the figure case i force is such that m is at rest relative to the wedge case ii force is such that wedge at rest relative to the ground Find the ratio of normal reaction between the wedge and the block in case i to case ii neglect friction between m and wedge 0 45

ra 2 1 Two blocks A and B attached to each other by a massless 2 spring are kept on a rough horizontal surface 0 1 and pulled by a force F 200 N as shown in the figure 2 132 If at some instant the 10 kg mass has acceleration of 12 m s what is the acceleration of 20 kg mass C A 2 5 m s C 3 6 m s B 10 kg mmmmmmmmmmmm 20 kg 0 1 Figure 2 132 F 200N B 4 0 m s D 1 2 m s

A uniform ring of mass m is placed on a rough horizontal fixed surface as shown in the figure The coefficient of friction between the left part of the ring and left part of the horizontal surface is 1 0 6 and between right half and the surface is 2 0 2 At the instant shown now the ring has been imparted an angular velocity in clockwise sense in the figure shown At this moment magnitude of acceleration of centre O of the ring in m s2 is take g 10 m s

A racing car moving towards a cliff sounds its horn The driver observes that the sound reflected form the cliff has a pitch one octave higher than the actual sound of the horn If V is the velocity of sound the velocity of the car will be 1 V 2 2 V 2 3 m V 3

The value of coefficient of friction is lowered on wetting the surface Assertion It is difficult to move a cycle along the road with its brakes on Reason Sliding friction is greater than rolling friction Assertion The driver in a vehicle moving with a constant speed on a straight r

A block has mass of 5 kg and is released from rest at the top of a frictionless slide It then enters a region with friction and comes to a stop The initial height is 2 m The mass travels 7 m through the friction zone before coming to a stop What is the value of the coefficient of kinetic friction Question 3 options 0 286 0 092 0 42 3 5 0 713

nless Two masses m 5kg and m 10kg connected by an inextensibl pulley are moving as shown in the figure The coefficient of friction of horizontal surface is 0 15 The maximum weight m that should be put on top of me to stop the motion is JEE Main 2018 T m T

In the arrangement shown W 200 N W 100 N and 0 25 for all surfaces in contact The work W just slide under the block W2 A a pull of 50 N is to be applied on W B a pull of 90 N is to be applied on W C tension in the string AB is 10 2 N D tension in the string AB is 20 2 N P W W A 45 B

SolveLancer Test A block is tied to a string and placed on a table as shown The table is pulled from below at a constant speed of 1 m s What is the angle the string makes with vertical Given 0 5 and tension in string is half the weight of block SolveLancer Test a 53 b 45 c 30 d 37 m v 1 m s

22 A block of mass m 0 1 kg is released from a height of 4m on a curved smooth surface On the horizontal surface path AB is smooth and path BC offers coefficient of friction 0 1 If the impact of block with the vertical wall at C be elastic the total distance covered by the block on the horizontal surface before coming to rest will be take g 10 m s a 29 m c 59 m 4m A 1m 33X B b 49 m d 109 m 2m W 98

Q10 A body of mass m is kept on a rough horizontal surface coefficient of friction A horizontal force is applied on the body but it does not move The resultant of normal reaction and the frictional force acting on the object is given by F where F is NEET ODISHA 2018 a F mg b F mg umg c F mg d F mg 1

Q12 A block of 10 kg mass is placed on a rough inclined surface as shown in figure The acceleration of the block will be 10 kg 30 mm a Zero b g c g 2 d 3 2 H 1 H 0 8

Q5 The coefficient of static friction us between block A of mass 2 kg and the table as shown in the figure is 0 2 What would be the maximum mass value of block B so that the two blocks do not move The string and the pulley are assumed to be smooth and massless g 10 m s CBSE AIPMT 2004 2 kg A a 0 4 kg b 2 0 kg c 4 0 kg d 0 2 kg TTC B

A particle mass m moves on a rough horizontal ground with some initial velocity say vo If 3 4 th of its kinetic energy is lost due to friction in time to then average power delivered by friction O O 3 mv 8 to 3 mv 4 to 1 mv 2 to 1 mv 4 to

17 A block is kept on a rough horizontal plank The coefficient of friction between the block and the plank is The plank is undergoing SHM of angular 2 frequency 10 rad s The maximum amplitude of plank in which the block does not slip over the plank is g 10 m s a 4 cm b 5 cm c 10 cm d 16 cm

Consider a solid sphere placed on an inclined plane The friction coefficient between the plane and the sphere is For which of the following cases will the friction acting on the sphere be dissipative r 0 2 0 30 0 25 0 45 0 2 0 37 0 6 0 53

A cylindrical vessel filled with water is released on an inclined surface of angle 0 as shown in figure The friction coefficient of surface with vessel is u tan 0 Then the constant angle made by the surface of water with the incline will be A tan u I B tan lu Fixed 00 C 0 tan D cot u

a A block weighing 1500 N overlying a 10 wedge on a horizontal floor and leaning against a vertical wall is to be raised by applying a horizontal force to the wedge Assuming the coefficient of friction between all the surfaces in contact to be 0 3 determine the minimum horizontal force required to raise the block

a The forces 20 N 30N 40N 50N and 60N are acting at one of the angular points of a regular hexagon towards the other five angular points taken in order Find the magnitude and direction of the resultant

If mass of the fissionable material is less than the critical mass then Question Type Single Correct Type 1 2 3 4 fission and chain reaction both are impossible fission is possible but chain reaction is impossible fission is impossible but chain reaction is possible fission and chain reaction both are

A block of mass 5 kg has given horizontal 41 velocity 31 41 m sec over rough horizontal surface along surface If coefficient of kinetic friction of surface is k 0 5 Find the friction force vector take g 10 m sec 1 61 81 3 121 18 2 151 20 4 15 20

meter and mass m 4 kg lies on the horizontal table Coefficient of friction between the rod and the table is 2 If the current in the conductor is 2 ampere then find the minimum magnitude of magnetic field strength in Tesla such that conducting rod just starts to translate along x axis take g 10 m s neglect the radius of rod M l

A slab of mass m 30 kg is kept over a smooth horizontal surface above which a block of mass m 10 kg has been kept as shown The coefficient of friction u between the block and the slab is 0 5 A horizontal force F acts on the block The value of F for which both the masses will move together is g 10 m s 1 50 N 100 N m m Smooth 2 F 200 3 N 1 All of these

A 20 kg box is gently placed on a rough inclined plane of inclination 30 with horizontal The coefficient of sliding friction between the box and the plane is 0 4 Find the acceleration of the box down the incline NK mgsina a mg F uN mgcosa X

1 54 A charge q is placed at the centre of the line joining two equal charges Q The system of the three charges will be in equilibrium ifq is equal to A C a a 2 PB D al 4 2

Two blocks of masses m and 2m are placed one over the other as shown in the figure The coefficient of friction between m and 2m is u and between 2m and ground is If a horizontal force F is applied on the upper block and T is the tension developed in the string then choose the incorrect alternative 1 If F mg T 0 2 If F umg T 0 3 If F 2umg Tumg 3 4 If F 3umg T 0 m 2m F AAJ KA TOPPER

A solid cylinder of mass m and radius r is rolling on a rough inclined plane of inclination 0 coefficient of friction between the cylinder and incline is Then 2 A frictional force is always mg cos 0 B friction is a dissipative force C by decreasing 0 frictional force decreases D friction opposes translation and supports rotation

A box weighing 6 kg is being pulled with an acceleration of 0 5 m s over a rough surface with the help of a string as shown in the diagram If the coefficient of kinetic friction involved is 0 5 then the tension in the string in N is 37

A block of 200 kg mass rests on a rough horizontal plane Find the force required each of the following cases i to just pull the block by a horizontal force P ii to just pull the block b an inclined force P inclined at 30 to the horizontal and iii to just push the block by a horizontal forc P The coefficient of static friction between the contact surfaces is 0 3 Fig 6 116 P 30 P

Pull 53 0 2 20 m 1 50 m A worker wants to turn over a uniform 1270 NN rectangular crate by pulling at 53 0 on one of its vertical sides Figure 1 The floor is rough enough to prevent the crate from slipping A What pull is needed to just start the crate to tip B How hard does the floor push upward on the crate Express your answer with the appropriate units C Find the friction force on the crate Express your answer with the appropriate units D What is the minimum coefficient of static friction needed to prevent the crate from slipping on the floor

A 29 A spring is cut into two parts in S length Find the stiffness constant of smaller part if stiffness constant of original spring is K 1 10K 2 K 10

In the arrangement shown in the figure sin 37 3 5 0 7 37 10 kg 4kg 1 direction of force of friction is up the plane 2 the magnitude of force of friction is zero 3 the tension in the string is 20 N 4 magnitude of force of friction is 56 N

4 4 m sec Block A of mass 35 kg is resting on a friction floor Another block B of mass 7 kg is res on it as shown in the figure The coecfficier static friction between the blocks is 0 5 w kinetic friction is 0 4 If a horizontal forc 100 N is applied to block B then the accelera of the block A will be g 10 ms 7kg B 7777 1 0 8 ms 2 35kg A 100N 77 2 2 4 ms 2

A 40 kg slab rests on a frictionless floor as shown in the figure A 10 kg block rests on the top of the slab The static coefficient of friction between the block and slab is 0 60 while the kinetic friction is 0 40 The 10 kg block is acted upon by a horizontal force 100 N If g 9 8 m s the resulting acceleration of the slab will be 100 N 1 1 m s 10 kg 40 kg A B 2 1 5 m s

9 The system is pushed by a force F as shown in the figure All surfaces are smooth except between B and C Friction coefficient between B and C is u Minimum value of F to prevent block B from downward slipping is 3 2 2m mg m 2m 2 2 mg 3 2 mg umg 4 umg

AP eSAT X 0 m 0 P A 0 40 m B 1 0 m C 2 5 m D 10 m 0 20 13 A block slides from rest with negligible friction down the track above descending a vertical height of 5 0 m to point P at the bottom It then slides on the horizontal surface The coefficient of friction between the block and the horizontal surface is 0 20 How far does the block slide on the horizontal surface before it comes to rest

s Calculate the contact force acting on the mass m 7 8 15 placed over the inclined plane of friction co efficient 0 5 as shown M O S ontact tore ing mg sen 1 mg 37 3 Zero m F 0 SX img cosso 2 mg cos 19 2 5 74 mg 221 MB 2 4 mg 5 3 8m

A solid cylinder of mass m is wrapped with an inextensible light string and is placed o a rough inclined plane as shown in the figure The frictional force acting between the cylinder and the inclined plane is 60 The coefficient of static friction us is 0 4

5 43 6 A motor car running at the rate of 7 ms 1 can be stopped by applying brakes in 10 m Show that total resistance to the motion when brakes are on is one fourth of the weight of the car aintain a

Q9 For the figure shown mA 10 kg mB 15 kg and F 90 N Acceleration of blocks A and B respectively H 0 4 A B H 0 2 a 2 m s2 3m s b 1 6 m s2 2m s c 1 6 m s 1 6 m s d 2 m s2 1 6m s F

In the diagram the variation of coefficient of friction of the surface is shown The external force F applied on board is equal to 2 Mg Now the board of mass M is gently pushed so that it starts moving The variation of acceleration a of board with respect to displacement x has been shown Find the value of tan0 tan 03 smooth a Best answer A 0 B C KAKAH D Coefficient of friction for A to B 3 B to C 2 C to D and remaining surface is smooth Ma 2 Mg X If the block has moved by distance x g 3 F smooth Mg 2 Mg 3 Mg 3 3 3l e x 2 g 3 g 3 3l a 2 g da 3 g dx 3l for 2nd and 3rd cells similarly tan 0 tan 0 tan 0 3 2 1 x

39 When a bicycle is pedalled the force of friction exerted by the ground on the two wheels is such that it acts In the backward direction on the front wheel and in the forward direction on the rear wheel 2 In the forward direction on the front wheel and in the backward direction on the rear wheel 3 In the backward direction on both wheels 4 In the forward direction on both wheels

A train weighing 1000 ton is moving on a horizontal track with a uniform velocity of 10 m s The total resistance to the motion of the train is 5 kgf per ton If g 10 m s2 then the power of the engine is 1 200 kW 3 500 kW 2 400 kW 4 800 kW

2 11 A body of mass 5 x 10 3 kg is launched up on a rough inclined plane making an angle of 30 with the horizontal Obtain the coefficient of friction between the body and the plane if the time of ascent is half of the time of descent Ans TO 3461

Exp 32 A block B is pushed momentarily along a horizontal surface with an initial velocity v If u is the coefficient of sliding friction between B and the surface block B will come to rest after a time 1 2 v g ug T AIPMT Prelims 2007 V u at V 0 at 4

Attempting to slide it across the floor you exert a horizontal pushing force P at a height y above the floor as in the figure If y is too large the refrigerator will tip instead of sliding Find the largest value of y that makes the refrigerator slide without tipping if its mass is M 116 kg its center of mass is located where d 0 37 m and h 0 95 m and the coefficient of static friction between the refrigerator and the floor is us 0 29 Hints Use the equilibrium conditions to place the refrigerator on the verge of both sliding and tipping but not doing either When the refrigerator is on the verge of tipping the normal force will act at its lower front corner Question 1 A refrigerator is at rest on a level floor Attempting to slide it across the floor you exert a horizontal pushing force P at a height y above the floor as in the figure If y is too large the refrigerator will tip instead of sliding Find the largest value of y that makes the refrigerator slide without tipping if its mass is M 116 kg its center of mass is located where d 0 37 m and h 0 95 m and the coefficient of static friction between the refrigerator and the floor is 0 29 2 pts Hints Use the equilibrium conditions to place the refrigerator on the verge of both sliding and tipping but not doing either When the refrigerator is on the verge of tipping the normal force will act at its lower front corner M cm