Friction Questions and Answers

33 A force F i 47 acts on block shown The force of friction acting on the block is y a i c 2 4i X 1 kg 0 3 b 1 8 d 3 F

The driver of a bus travelling with a speed v suddenly observes a wall in front of his bus at a distance a Father of this driver who was also a driver had advised him to take a circular turn to avoid hitting in such a situation However the driver in question decides otherwise by using his own wisdom He applies brakes as hard as possible without taking a circular turn then 1 he is more likely to hit the wall 2 he is less likely to hit the wall 3 he is as likely to hit the wall 4 none of the above

A body starts from rest on a long inclined plane of slope 45 The coefficient of fiction between the body and the plane varies as 0 3 x where x is the distance travelled down the plane The body will have maximum speed for g 10 m s when x 1 9 8 m tang M 2 12 m 3 12 m 4 3 33m tan 45 0 3x x 100 2013

A block is placed on a rough horizontal plane A time dependent horizontal force F kt acts on the block where k is a positive constant The acceleration time graph of the block is JEE Main ONLINE 2013 14 2 3 D 4

0 278 A truck is carry a box of mass m 50 kg on its flat horizontal rough surface with coefficient of friction 0 3 It is crossing a circular track of radius 27 m What is the maximum speed of the truck so that the box does not slide from the truck while moving on the circular path m 1 18 km hr 3 32 4 km hr R 2 36 km hr 4 None of these

3 Two bodies of masses 1 Kg and 2 Kg a connected by a metal wire shown in figur force of 10N is applied on the body of mas Kg The breaking stress of metal wini 2x10 Nm The minimum radius of the sin used if it is not to break IKg 1 0 23x10 m EKGF 10N 2 4x10m

On the horizontal surface of a truck a block of mass 1 kg is placed 0 6 and truck is moving with acceleration 5 m s then the frictional force on block will be A 5N B 6N C 5 88N D 8N

67 If coefficient of friction between all surfaces is 0 4 then find the minimum force F to have equilibrium of the system Take g 10 ms a 62 5 N c 135 N Wall 25 kg VI 15 kg F b 150 N d 50 N

A cord passing over a pulley connects two masses as shown where m 3 10 kg and m 6 00 kg The system accelerates with a magnitude of 0 97 m s2 The coefficient of kinetic friction between the masses and the incline is the same for both masses Assume the pulley is frictionless and the cord is massless Due to the nature of this problem do not use rounded intermediate values in your calculations including answers submitted in WebAssign m 35 0 m 35 0 a What is the coefficient of kinetic friction b What is the tension in N in the cord N

A body of mass 2 kg is lying on a rough inclined plane of inclination 30 Find the magnitude of the force parallel to the incline needed to make the block move a up the incline b down the incline Coefficient of static friction 0 2 7 Repeat part a of problem 6 if the push is applied horizontally and not parallel to the incline

Which of the following forces is not conservative A F 3i 4 C F 3yi 4xj B F 3xi 4yi D F 3x 1 4y j on raxis has potential energy U 2 20 X 5x2 Joules along x axis The particl

and the block is 0 25 and that between the hand and the block is 0 15 what force must he exert Ans 5 kg wt A man lifts a 16 kg can of oil by pressing his two hands towards each other against the rough sides If the co efficient of static friction is 0 25 what force must he apply with each hand Ans 32 kg wt A man weighs 70 kg What is the greatest weight he can pull along a horizontal floor by a horizontal mp

spring is 100 N m Extension produced in the spring in equilibrium is g 10 m s 1 10 cm 3 30 cm 3Kg reelle 3Kg 2 20 cm 440 cm

View In English The system is pushed by a force F as shown in 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 A B m F 2m 1 3 4 36535550 2 2 mg mg mg mg 2m

A block is projected up along the line of greatest slop of an inclined plane of angle of inclination 0 0 wher o angle of friction Which of the following friction time graph is correct f gro 04 tint 3 O f f f 2 O El C f 4 0 20 t t

Example 10 39 Light source of wavelength 400 nm used in Lloyd s mirror lies 1 mm above the plane mirror Find the distance of first minima above the mirror Distance of the screen from the plane of the sources is 2 m

8 A triangular prism of mass M with a block of mass m placed on it is released from rest on a smooth inclined plane of inclination 0 The block does not slip on the prism Then e M Smooth Fig 7 296 a The acceleration of the prism is g cos 0 b The acceleration of the prism is g tan 0 c The minimum coefficient of friction between the block and the prism is min cot 0

ladder N Mg 14 The door of an almirah is 6 ft high 15 ft wide and weighs 8 kg The door is supported by two hinges situated at a distance of 1 ft from the ends If the magnitudes of the forces exerted by the hinges on the door are equal find this magnitude 53 A b angu ball pul If mor

DIOCK OI kg is lying on horizontal surface The static friction between the block and the surface of table is 0 5 What is the minimum value of force for motion of the block A 3 43 N C 343 No B 34 3 N D 3430 N

Example 6 12 In the arrangement shown in figure JA 4 0 kg and mg 1 0kg 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 1m Find the coefficient of friction between the block and the table Neglect friction elsewhere Take g 10 m s Solution From constraint relations we can see that VA 2VB Therefore 19 2 03 06ml A Fig 6 2

41 A block of mass 10 kg is moving on a rough surface as shown in figure The frictional force acting on block is v 4 m s 1 20 N 3 40 N TTTTT 0 6 10 kgh 2 4 F 20 N 60 N 80 N

1 700 N 2 1050 N A body is projected up a rough inclined plane from the bottom with some velocity It travels up the inclin and then returns back If the time of ascent is t and time of descent is t then 4 data insufficient 2 t t 3 t t 1 t t block of mass 9 1 kg is held against a wall by applying a horizontal force of 5N on the block If the co efficie of frictional force acting on the block is g

1 4 9 m s 2 9 8 m s 3 2 A body of mass 100 g is sliding from an inclined plane of inclination 30 What is the frictional force experienced if 1 7 Fr mgsing 0 1x 0x 101 5 1 7 N 1 5 21 7x N 13 17 5 N 1 7x 4 1 7 2 1 N 59 night horizontal road with a speed vo If the coefficient of friction between the tyres aned is

0 33 2 0 25 A block of mass 1 kg lies on a horizontal surface in a truck The coefficient of static friction between the bloc and the surface is 0 6 If the acceleration of the truck is 5 m s the frictional force acting on the block is 5 N 26 N 3 10 N 4 15 N A block of mass 2 kg rests on a rough inclined plane making an angle of 30 with the horizontal The coefficien The frictional force on the block is g 9 8m s 07

A block A kept on an inclined surface just begins to slide if the inclination is 30 The block is replaced by ar block B and it is found that it just begins to slide if the inclination is 40 1 mass of A mass of B 2 mass of A mass of B mass of B 3 mass of A 4 all the three are possible

1 4 Equal to the limiting force 3 scalar quantity A block is placed on a rough floor and a horizontal force F is applied on it The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them a The graph is a straight line of slope 45 b The graph is straight line parallel to the F axis e The graph is a straight line of slope 45 for small F and a straight line parallel to the F axis for large F There is small kink on the graph 1 c d 2 a d 3 a b a c lide if the inclination is 30 The block is replaced by another

The coefficient of static friction between two surfaces depends on Nature of surfaces 2 The shape of the surfaces in contact 3 The area of contact 4 All of the above I

Mark the correct statements about the friction between two bodies a static friction is always greater than the kinetic friction b coefficient of static friction is always greater than the coefficient of kinetic friction c limiting friction is always greater than the kinetic friction d limiting friction is never less than static friction 2 a b c b c d 3 a c d The coefficient of static friction between two surfaces depends on 4 a b d

S 13 How large must F be in figure to give 700 g block an acceleration of 30 cm s The coefficient of friction between the two blocks and also between the block and the table is 0 15 200 g 700 g

All surfaces are rough What should be the maximum coefficient of friction between block A and the surface under it so that all the blocks move together A 0 25 C 0 20 B 0 5 D the block of mass 4m will never move A mass mass

A body of mass M is kept on a rough horizontal surface friction coefficient A person is trying to pull the body by applying a horizontal force but the body is not moving The force by the surface on A is F where a F Mg b F Mg 2 d Mg F Mg 1 2 X Mg F Mg V1 u

In the system shown in figure tension T2 is xg then what s the value of x g 10 m s T q g 3 700 Ts 1 kg AT2 2 kg AT 3 kg

2 While walking on ice one should take small steps to avoid slipping This is because smaller steps ensure a larger friction b smaller friction c larger normal force d smaller normal force

L 4 and m of different Three blocks A B and C of mass m 2 densities and dimensions are placed over each other as shown in the figure The coefficients of friction are shown Blocks placed in a vertical line are made to move towards right with same velocity at the same instant Find the time in sec taken by the upper block A ta L topple from the middle block B Assume that blocks B and C don t stop sliding before A topples from B given L 36 m 0 4 and g 10 m s L 2 2 B C

estion 39 d the value of frictional resistance if the dy is in limiting equilibrium Refer owing figure ote Click on image to enlarge it 400 N 46 14 N 00 00 N 200 N O P cos 30 O 400 cos 30 R

Question 11 If frictional force is 100N and the normal reaction is 200N then the resultant reaction is 300N 150N 322 16N 00

Assertion Magnitude of the contact force is always greater than the magnitude of frictional force Reason Contact force is the resultant of the friction force and normal reaction

Maximum acceleration of the train at which a box lying on its floor will remai stationary with respect to floor coefficient of friction between box and floor below the box is 0 25 is 2 9 ms 2 1 7 ms 2 O2 45 ms 2 16 mr 2

The maximum speed with which a car is driven round a curve of radius 12 5 without skidding with coefficient of friction between tyres and roadway 0 2 is 12 km hr 1 16 km hr 1 18 km hr 1 36 km hr 1

A suitcase is gently dropped on a conveyor belt moving at 3 m s If the coefficient of friction between the belt and the suitcase is 0 5 find the displacement of the suitcase relative to conveyor belt before the slipping between the two is stopped g 10 m s 3 m s g 10 m s af de A 2 7m B 1 8m C 0 9m D 1 2m fr faze

d A parallel plate capacitor of capacitance C is as shown A thin metal plate A is placed between the plates of the given capacitor in such a way that its edges touch the two plates as shown The capacity now be comes 44

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

A block of mass 1 kg is horizontally thrown with velocity of 10 m s on a stationary long rough plank whose coefficient of kinetic friction is 0 25 After what time block will come to

A block of mass 50 kg is projected horizontally on a rough horizontal floor The coefficient of friction between the block and the floor is 0 1 The block strikes a light spring of stiffness k 100 N m with a velocity 2m s The maximum compression of the spring is 1 Im 2 2 m 2m s 50 kg 800 0 1 3 3 m 4 4 m quitance depends on

The work done by the frictional force on a surface in drawing a circle of radius r on the surface by a pencil of negligible mass with a normal pressing force N coefficient of friction H is 1 4 r N 2 2 r N 3 2 N 4 zero A force F 5 2x acts on a body in x direction where x is in metres and F in newton Find the work done in displaci

60 3 Three identical balls A B and C each of mass m 3 kg are connected by strings AB and BC as The whole system is placed on a smooth horizontal surface Now the ball B is given an initial velocity v perpendicular to the strings and along the horizontal surface Find the tension in Newton in the string just be the balls A and C collide BMR Doubt 1m Im

4 A box of mass 20 kg is connected to mass of 2 kg hanging through a light string and an ideal pulley as shown in figure Coefficient of kinetic friction between trolley and surface is 0 05 What is acceleration of the box g 10 m s 20 kg Box TITT RATTAKENTEENTHETT

Identify the correct statement O Kinetic friction depends on area of contact for a given normal contact face O Coefficient of kinetic friction is generally less than coefficient of static friction O The magnitude of kinetic friction cannot be more than static friction Coefficient of static friction does not depend on surface nature in contact

26 kg block is connected to a 78 78 kg block by a string The blocks are sliding across a surface where the coefficient of kinetic friction is 0 0 0 06 a What is the magnitude of the common acceleration of the blocks m s2 b What is the tension in the string

t 0 98 m s m s A body A of mass 1kg rests on a smooth surface Another body B of mass 0 2 kg is placed over A as shown The coefficient of static friction between A and B is 0 15 B will being to slide on A if a pulled with a force greater than 1 764 N B A 2 0 1764 N