EASY

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The shortest distance (in metres) in which an automobile moving at a speed of $90 km h^{- 1}$ can be stopped while travelling on a road whose coefficient of kinetic friction is $0.2$ is $P$ metres. Then, the value of $\frac{P}{10}$ is ( Approximate to the nearest integer): (Take $g = 10 m s^{- 2}$ )

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Important Questions on Friction

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A block of mass $5 kg$ is kept against an accelerating wedge with a wedge angle of $45 °$ to the horizontal. The co-efficient of friction between the block and the wedge is $μ = 0.4$ . What is the minimum absolute value of the acceleration of the wedge to keep the block steady. Assume $g = 10 m s^{- 2}$

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MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A block of mass

m

is placed on a surface with a vertical cross section given by

y = \frac{x^{3}}{6}

. If the coefficient of friction is

0.5

, the maximum height above the ground at which the block can be placed without slipping is

HARD

Physics>Mechanics>Friction>Dynamic Friction

Put a uniform meter scale horizontally on your extended index fingers with the left one at

0.00 cm

and the right one at

90.00 cm

. When you attempt to move both the fingers slowly towards the center, initially only the left finger slips with respect to the scale and the right finger does not. After some distance, the left finger stops and the right one starts slipping. Then the right finger stops at a distance

x_{R}

from the center

(50.00 cm)

of the scale and the left one starts slipping again. This happens because of the difference in the frictional forces on the two fingers. If the coefficients of static and dynamic friction between the fingers and the scale are

0.40

and

0.32

, respectively, the value of

x_{R}

(in cm) is___________.

EASY

Physics>Mechanics>Friction>Dynamic Friction

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 is

(g = 10 m s^{- 2})

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A car is negotiating a curved road of radius

R

. The road is banked at an angle

θ

. The coefficient of friction between the tyres of the car and the road is

μ_{s}

. The maximum safe velocity on this road is:

EASY

Physics>Mechanics>Friction>Dynamic Friction

A block is released from rest on a

45 °

smooth incline and slide a distance

d

. The time taken to slide the same distance is

n

times as much to slide on a

45 °

rough incline than on the smooth incline. The coefficients of friction for the rough incline is

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A heavy box is to be dragged along a rough horizontal floor. To do so, the person

A

pushes it at an angle

30 °

from the horizontal and requires a minimum force

F_{A}

, while the person

B

pulls the box at an angle

60 °

from the horizontal and needs minimum force

F_{B}

. If the coefficient of friction between the box and the floor is

\frac{\sqrt{3}}{5}

, the ratio

\frac{F_{A}}{F_{B}}

EASY

Physics>Mechanics>Friction>Dynamic Friction

A block placed on the horizontal is pushed momentarily with initial velocity

v

. The coefficient of friction between the block and surface is

μ

. Block will come to rest after a time

t

equal to (

g =

acceleration due to gravity)

HARD

Physics>Mechanics>Friction>Dynamic Friction

A box when dropped from a certain height reaches the ground with a speed

v

. When it slides from rest from the same height down a rough inclined plane inclined at an angle

45^{o}

to the horizontal, it reaches the ground with a speed

\frac{v}{3}

. The coefficient of sliding friction between the box and the plane is (acceleration due to gravity is

10 m s^{- 2}

)

HARD

Physics>Mechanics>Friction>Dynamic Friction

A small box resting on one edge of the table is struck in such a way that it slides off the other edge,

1 m

away, after

2

seconds. The coefficient of kinetic friction between the box and the table

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A uniform chain of length

L

is lying partly on a table, the remaining part hanging down from the edge of the table. If the coefficient of friction between the chain and the table is

0.5,

what is the minimum length of the chain that should lie on the table, to prevent the chain from slipping down to the ground?

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

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:
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EASY

Physics>Mechanics>Friction>Dynamic Friction

Meena applies the front brakes while riding on her bicycle along a flat road. The force that slows her bicycle is provided by the

EASY

Physics>Mechanics>Friction>Dynamic Friction

A body of mass

2 kg

is kept by pressing to a vertical wall by a force of

100 N

. The friction between wall and body is

0.3

. Then the frictional force is equal to

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

An inclined plane is bent in such a way that the vertical cross-section is given by

y = \frac{x^{2}}{4}

, where

y

is in vertical and

x

in horizontal direction. If the upper surface of this curved plane is rough with coefficient of friction

μ = 0.5,

the maximum height in

cm

at which a stationary block will not slip downward is________

cm .

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A body of mass

1 kg

rests on a horizontal floor with which it has a coefficient of static friction

\frac{1}{\sqrt{3}}

. It is desired to make the body move by applying the minimum possible force

F N

. The value of

F

will be _______.(Round off to the Nearest Integer) [Take

g = 10 {m s}^{- 2}

]

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A block of mass $m$ slides along a floor while a force of magnitude $F$ is applied to it at an angle $θ$ as shown in figure. The coefficient of kinetic friction is $μ_{K}$ . Then, the block's acceleration $a$ is given by : ( $g$ is acceleration due to gravity)

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EASY

Physics>Mechanics>Friction>Dynamic Friction

A block A of mass 4 kg is placed on another block B of mass 5 kg, and the block B rests on a smooth horizontal table. If the minimum force that can be applied on A so that both the blocks move together is 12 N, the maximum force that can be applied on B for the blocks to move together will be :

MEDIUM

Physics>Mechanics>Friction>Dynamic Friction

A block

A

of mass

m_{1}

rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block

B

of mass

m_{2}

is suspended. The coefficient of kinetic friction between the block and the table is

μ_{k}

. When the block

B

is sliding on the table, the tension in string is:

EASY

Physics>Mechanics>Friction>Dynamic Friction

Given in the figure are two blocks

A

and

B

of weight

20 N

and

100 N

, respectively. These are being pressed against a wall by a force

F

and kept in equilibrium as shown. If the coefficient of friction between the blocks is

0.1

and between block

B

and the wall is

0.15

, the frictional force applied by the wall on block

B

is:

The shortest distance (in metres) in which an automobile moving at a speed of 90 km h-1 can be stopped while travelling on a road whose coefficient of kinetic friction is 0.2 is P metres. Then, the value of P10 is ( Approximate to the nearest integer): (Take g=10 m s-2)

Important Questions on Friction

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