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A block is placed over a plank. The coefficient of friction between the block and the plank is $μ = 0.2$ . Initially both are at rest, suddenly the plank starts moving with an acceleration $a_{0} = 4 m s^{- 2}$ . The displacement of the block in $1 s$ is $(g = 10 m s^{- 2})$

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Important Questions on Friction

EASY

Physics>Mechanics>Friction>Friction

A block of mass

10 kg

starts sliding on a surface with an initial velocity of

9.8 {ms}^{- 1}

. The coefficient of friction between the surface and block is

0.5

. The distance covered by the block before coming to rest is :[use

g = 9.8 {ms}^{- 2}

]

MEDIUM

Physics>Mechanics>Friction>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)

Question Image

EASY

Physics>Mechanics>Friction>Friction

What is the maximum force

F

that can be applied on block

m_{1},

so that both

m_{1} & m_{2}

will move together? There is no friction between

m_{1}

and the horizontal table. The coefficient of friction between

' m_{1}'

and

' m_{2}'

μ .

EASY

Physics>Mechanics>Friction>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:

MEDIUM

Physics>Mechanics>Friction>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>Friction

Which of the following is a self adjusting force?

MEDIUM

Physics>Mechanics>Friction>Friction

A solid cylinder of mass $m$ is wrapped with an inextensible light string and, is placed on a rough inclined plane as shown in the figure. The frictional force acting between the cylinder and the inclined plane is:

Question Image

[The coefficient of static friction, $μ_{s}$ , is $0.4$ ]

MEDIUM

Physics>Mechanics>Friction>Friction

The following observations were taken for determining surface tension

T

of water by capillary method:

diameter of capillary,

D = 1.25 \times 10^{- 2} m

rise of water,

h = 1.45 \times 10^{- 2} m

Using

g = 9.80 m s^{- 2}

and the simplified relation

T = \frac{r h g}{2} \times 10^{3} N m^{- 1}

the possible error in surface tension is closest to:

MEDIUM

Physics>Mechanics>Friction>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?

EASY

Physics>Mechanics>Friction>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

HARD

Physics>Mechanics>Friction>Friction

Assume that a drop of a liquid evaporates by a decrease in its surface energy so that its temperature remains unchanged. The minimum radius of the drop for this to be possible is. (The surface tension is

T

, the density of the liquid is

ρ

and

L

is its latent heat of vaporisation.)

HARD

Physics>Mechanics>Friction>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___________.

MEDIUM

Physics>Mechanics>Friction>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>Friction

Which one of the following statements is incorrect?

EASY

Physics>Mechanics>Friction>Friction

A rectangular film of liquid is extended from

(4 cm \times 2 cm)

(5 cm \times 4 cm)

. If the work done is

3 \times 10^{- 4} J

, the value of the surface tension of the liquid is

HARD

Physics>Mechanics>Friction>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

EASY

Physics>Mechanics>Friction>Friction

When one end of the capillary is dipped in water, the height of the water column is

h

. The upward force of

105 dyne

due to surface tension is balanced by the force due to the weight of the water column. The inner circumference of the capillary is
(Surface tension of water

= 7 \times 10^{- 2} N m^{- 1})

MEDIUM

Physics>Mechanics>Friction>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 .

HARD

Physics>Mechanics>Friction>Friction

A block of mass

100 kg

attached to a massless rope and the second end of the rope is pulled up by

2

men along a rough inclined plane of coefficient of friction

0.2

inclined at

37 °

with the horizontal. If they exert their maximum force for the block to just start moving up, the force exerted by each of them is, (Acceleration due to gravity

= 10 m s^{- 2}, \tan 37 ° ≃ 0.75

)

MEDIUM

Physics>Mechanics>Friction>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

A block is placed over a plank. The coefficient of friction between the block and the plank is μ=0.2. Initially both are at rest, suddenly the plank starts moving with an acceleration a0=4 m s-2. The displacement of the block in 1 s is g=10 m s-2

Important Questions on Friction

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A block is placed over a plank. The coefficient of friction between the block and the plank is $μ = 0.2$ . Initially both are at rest, suddenly the plank starts moving with an acceleration $a_{0} = 4 m s^{- 2}$ . The displacement of the block in $1 s$ is $(g = 10 m s^{- 2})$