Friction Questions and Answers

1 Temperature 3 Cohesive force 4 The inclination of surface 31 When a capillary tube is immersed in a liquid then liquid of mass M rises in the capillary tube If capilla tube of double radius is taken then mass of same liquid rising in the tube is 1 M 2 2 2 M 3 M 4 4 4 M

ATION 16 A B 2kg 4kg frictionless 0 5 F ind out the maximum value of F for which both the blocks will move

Let f x be a function satisfying f x f x with f 0 1 and g be the functie satisfying f x g x x The value of the integral f f x g x dx is b e e 3 1 a e 1 c e 3 2 e 5 11 2 d e 1 3 e 2 1

A half section of a uniform hollow sphere of mass m is at rest A force 5F is applied from inner side of sphere as shown in figure Assume that the section rolls without slipping The minimum value of s compatible with the motion is K 20 Find the value of K Take F mg

A small block of mass m is projected with a speed 2 m s on a horizontal smooth floor which merges into a rough horizontal circular ring in shape of a quarter circle and moves along its inside as shown in the figure The coefficient of friction between the block and circular path is 0 2 If the radius of the circular path is 2 m then the speed of the block when it reaches end of circular path is the figure shows top view take e 0 73 1 0 57 m s 2 1 1 m s

A ray of light moving along the unit vector i 2j undergoes refraction at an interface of two media which is the x z plane The refractive index for y 0 is 2 while for y 0 it is 5 2 The unit vector along which the refracted ray moves is A 31 51 34 B 4i 3i 5 31 41 C 31 5 D None of these

of kinetic friction between the body and the inclined plane sin 37 3 5 Ans 0 67 24 The minimum force required to move a block up a rough plane inclined at an angle of 30 to the horizontal was found to be five times the minimum force needed to move the block down the plane If the force act parallel to the plane find the co efficient of fricition between the plane and the block Ans 0 866 28 A block is projected up a plane inclined at 30 to the horizontal It returns to its starting point with

3 Iwo blocks are connected by a rope of negligible mass as shown The lower block has mass my and the coefficient of kinetic friction between this block and the incline of angle is The upper block has mass m2 and the coefficient of kinetic friction between this block and the incline of angle Ois 2uk When released from rest the two blocks accelerate together down the incline and the rope remains stretched The magnitude of the acceleration due to gravity is g which is a positive quantity Mass m Coefficient of kinetic friction 2 Rope 0 Mass m Coefficient of kinetic friction p Direction of motion Acceleration of blocks Tension in rope a Draw two free body diagrams one for the block of mass m and one for the block of mass m On each diagram label each force with what kind of force it is gravitational normal etc and what object exerts that force b Find the magnitude of the acceleration of the two blocks Assume that the values of mi m p g and are known quantities c Find the tension in the rope Assume that the values of m m k g and are known quantities

If two S H M are represented by equations y 10 sin 3nt TL 4 and Y 5 sin 3 t 3 cos 3rt then find the ratio of their amplitudes and phase difference in between th

Two blocks are connected over a massless pulley as shown in figure The mass of block A is 10 kg and the coefficient of kinetic friction is 0 2 Block A slides down the incline at constant speed The mass of block B in kg is a 5 4 c 4 2 30 A b 3 3 d 6 8 B

Ball 1 has a mass m 0 4 kg Ball 2 has a mass m 0 2 kg and Ball 3 has a mass m 0 3 kg Ball 1 is initially moving to the right with a speed v 2 m sec Ball 1 then collides with Ball 2 and Ball 3 After the collision Ball 1 is moving to the left with a speed v 0 5 m sec After the collision Ball 2 moves at an angle of 35 above the horizontal with a speed 12 After the collision Ball 3 moves at an angle of 20 below the horizontal with a speed 13 a What is t2 the speed of my after the collision b What is v3 the speed of my after the collision c What is KE the kinetic energy of the 3 ball system before the collision d KEJ the kinetic energy of the 3 ball system after the collision Vi my Initial mz m3 V1 1 m Final m M3 12 35 20 V3

how far will it rise be A body is pushed up an inclined plane with an initial velocity of 14 6 m s It takes 2 s to reach its maxi mum height How much time will it take to slide down What distance did the body cover Find the coefficient of sliding friction between the body and the inclined plane Given the angle of inclination of the plane is 3 42 s 14 6 m 0 2831

1 A block of mass 25 kg is lying on an inclined plane of angle 30 In order to make it move upward along the slope with an acceleration of 20 cm s a horizontal force of 250 N is required to be applied on it Calculate i frictional force on the block and ii coefficient of kinetic friction

5 A man manages to balance a block of mass 2 kg by pushing it horizontally against an erect wall If 0 25 between the wall and the block and 0 15 between the block and the hand find the 49 N force needed to be applied by the man

1 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 0s The coefficients of static and kinetic friction between the box and the plank will be respectively 1 0 4 and 0 3 2 0 6 and 0 6 3 0 6 and 0 5 4 0 5 and 0 6 mg 0 S

6 Five vectors X Y Z OB and AO are connected as shown in figure If OB AO then which of the following option is correct o 1 X Y 2Z 3 X Y 3 Z B O A 2 X 2 4 2X

Two object each of mass 40 kg rests on two rough inclined planes having inclination 30 and 37 respectively If coefficients of friction for these surfaces are 0 6 and 0 8 respectively then ratio of friction force acting on these surfaces are 1 1 1 2 3 5 3 5 6 4 15 3 32

A block of mass 4 kg is placed over another block of mass 5 kg The 5 kg block is placed over smooth plane while coefficient of friction between two blocks is 0 4 The maximum horizontal force F for which two blocks will move together will be P 0 4 smooth 1 16 N 3 24 8 N 4 kg 10 5 kg 20 F 16 20 8 N 4 28 8 N 20

14 A system consists of three masses m m and m3 connected by a string passing over a pulley P The mass m hangs freely and m and m3 are on a rough horizontal table The coefficient of friction The pulley is frictionless and of negligible mass The downward acceleration of mass m is Assume m m m m AIPMT 2014 m m3 P 1 2 g 1 gu 9 g 1 2 m 5 2 4 2g 3 g 1 2

1 Refractive index of violet yellow and Red colour of light for a material of lens are 1 66 1 64 1 62 respectively If mean focal length of lens is 10cm Then chromatic abberation between the colour of violet and red will be 1 0 625 cm 3 02 cm 2 0 125 m 4 0 cm

In the figure shown there is a block of mass 4kg kept over a block of mass 6kg Coefficient of friction between block is and between block and ground is then minimum ratio of P H move together is 77 4 6 so that the masses 1 F H 5 H2

A block is placed on a rough plane whose inclination to the horizontal 0 can be varied The angle of repose is 30 The graph that correctly indicates the variation of the frictional force f between the block and the plane with 0 is Mk S 1 3 T 30 0 0 2 4 f f 30 30 0

43 A block of mass 4 kg is placed on a rough fixed inclined plane as shown The minimum force F which is parallel to inclined to keep the block at rest is g 10 m s 1 20 2 N 3 20 N Rough 0 5 0 45 2 Zero

A uniform rod of length 2 and mass m is suspended from one end by inextensible string and other end lies on smooth ground The angle made by rod with vertical is 0 sin 1 3 If N and N represents the contact force from ground on rod just before and just after cutting string then find the ratio of N N 20

A solid onere rough surface as shown in figure Two forces having magnitude 2F and F are applied as shown If the sphere performs pure rolling along right direction then frictional force acting on the sphere is O F 1 In forward direction 2 In backward direction 3 Zero Can t he predicted 2F

0 A block of mass 2 kg is pulled along a horizontal surface by applying a force at an angle 30 with the horizontal If the block travels with a uniform velocity and has a displacement 115 cm and the coefficient of friction is 0 15 then the work done by the applied force is 1 3 2 J 3 32 J 2 320 J 4 0 32 J

2 If a pushing force making an angle a with horizontal is applied on a block of mass m placed on horizontal table and angle of friction is B then minimum magnitude of force required to move the block is 1 2 3 4 mg sin cos B mg sin cos B mg sin sin a B mg cos corla B1

mple 12 A 1000 kg engine pulls a train of 4 wagons each of 2500 kg along a horizontal railway track If the engine exerts a force of 50000 N on wagons and track offers force of friction 2500 Na each wagon then calculate The net accelerating force The acceleration of the train i ii iii The force of wagon 1 on wagon 2

A 40 kg slab B rests on a smooth floor as shown in figure A 10 kg block A rests on the top of the slab The static coefficient of friction between slab and block is 0 6 while the kinetic friction coefficient is 0 4 The block A is acted upon by a horizontal force 100 N If g 9 8 m s2 the resulting acceleration of the slab B will be No friction 1 0 98 m s 100N 10 kg A 40 kg B 2 1 47 m s2

iii Two block system on a F M M M M g both blocks move together with acceleration a F M M with a max HM M b F H M M M 9 relative sliding starts M g M moves with constant acceleration a H M g M F u M g M M Smooth F

A spring of force constant k 300 N m connects two blocks having masses 2 kg and 3 kg lying on a smooth horizontal plane If the spring block system is released from a stretched position find the number of complete oscillations in 1 minute Take 10 T

Illustration 44 In a hemispherical bowl of radius r there is an insect at its bottom Coefficient of friction between the insect and the surface of the bowl is u Find the height upto which the insect can crawl

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 2 8080 BA NURTURE PHY ENG MODULE 01104 NUM 02

17 A small block of mass m is moved on a rough hemisphere with the help of string as shown in the figure The work done by friction on the block as it moves from position A to position B is Coefficient of friction is m A 1 mgR 3 mgR B R R F 2mg 2 mg R 4 2 mgR

A block of mass 1 kg is placed on the rough horizontal surface of a car moving with constant acceleration a 2m s starting from rest as shown The net work done by frictional force on the block relative to ground in first 4 sec is 0 4 3 HF0 3 1 kg a 2m s A

It the coefficient of friction between the block of mass 5 kg and wall is 0 5 then minimum force F required to hold the block with the wall is g 10 m s NCERT Pg 101 1 10 N 3 40 N F 5 kg 0 5 T 2 100 N 4 50 N

Two cars of unequal masses use similar tyres If they are moving with same initial speed the minimum stopping distance 1 Is smaller for the heavier car 2 Is smaller for the lighter car 3 Is same for both the cars

The car A is used to pull a load B with the pulley arrangement shown If A has a forward velocity v determine an expression for the upward velocity vg of the load in terms of V and 0 0 is angle between string and horizontal B A A V C B V sin 0 cos e C VA cos 0 D 1 V tan 0

4 A implied B and B implies A 29 In the figure shown the friction coefficient between the block of mass 1 Kg and the plank of mass 2 Kg is 0 4 while that between the plank and floor is 0 1 A constant force F starts acting horizontally on the upper 1 Kg block The acceleration of plank if F 10 N is 1 10 3 m s 2 7 3 m s 3 0 5 m s 1 kg 2 kg 4 1 0 m s LL

7 Two blocks of mass 1 kg each are joined by a string and placed on two inclined planes The string passes over a pulley Fig 2 43 Coefficient of friction between the blocks and the two planes is 0 1 Find i acceleration of the system and ii tension in the string 1 kg 45 Fig 242 1 kg 30 10211 2 6 NI

An insect of mass m 3 kg is inside a vertical drum of radius 2 m that is rotating with an angular velocity of 5 rad s The insect doesn t fall off Then the minimum coefficient of friction required is a 0 5 b 0 4 c 0 2 d None of the above guy ex is to suit w

inclination 30 The friction coefficient between the block of mass 2 0 kg and the incline is ows two blocks in contact sliding down an inclined surface of 0 20 and that between the block of mass 4 0 kg and the incline is 0 30 Find the acceleration of 2 0 kg block g 10 m s 4kg 2kg

At what height should a rope of length x be tied to a long vertical pole so that a person standing on the ground can pull down the pole by applying a force F at the other end of the rope most conveniently

5 A 40 kg slab rests on a frictionless floor A 10 kg block rests on top of the slab The coefficient kinetic friction between the block and the slab is 0 40 A horizontal force of 100 N is applied on the 10 kg block Find the resulting acceleration of the slab g 10 ms a 3 ms c 1 ms b 4 ms d 2 ms

43 Two blocks A of 6 kg and B of 4 kg are placed in contact with each other as shown in Fig 7 291 F Smooth A 6 kg 1 Smooth 37 Rough Fig 7 291 B 4 kg 1 0 5 There is no friction between A and ground and between both the blocks The coefficient of friction between B and ground is 0 5 A horizontal force F is applied on A Find the minimum and maximum values of F which can be applied so that both blocks can move combinely without any relative motion between them a 10 N 50 N b 12 N 50 N d None of the C 12 N 75 N

5 A standing sound wave in a pipe has displacement nodes and five antinodes The harmonic number of vibrations is 1 3 3 5 2 4 4 9 boook you 2010

A block of mass 20kg is placed on a rough horizontal plane and a horizontal force of 12N is applied If coefficient of friction is 0 1 the frictional force acting on it is 1 20 N 2 12 N 3 8 N 4 28 N

In which of the following cases frictional force is impulsive A C 0 0 M v 0 m B D H 0 All of these V O

IF 0 4 01 1777 7 kg 35 kg F H 77 FA 7 If a force F of 100 N is applied to block of ma 7 kg then acceleration of 35 kg mass will be

When a body of mass 120 g resting on a horizontal plane is pulled by a rope inclined at an angle 30 with the horizontal it acquires a velocity of 9 8 m s 1 in 10 s If the tension in the string is 0 588 N what is the coef ficient of sliding friction g 9 8 m s 2 CARE 0 44 long