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Important Questions on Mechanical Properties of Fluids

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Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

Two spheres

P

and

Q

of equal radii have densities

ρ_{1}

and

ρ_{2}

, respectively. The spheres are connected by a massless string and placed in liquids

L_{1}

and

L_{2}

of densities

σ_{1}

and

σ_{2}

and viscosities

η_{1}

and

η_{2}

, respectively. They float in equilibrium with the sphere

P

L_{1}

and sphere

Q

L_{2}

and the string being taut (see figure). If sphere

P

alone in

L_{2}

has terminal velocity

{\vec{V}}_{P}

and

Q

alone in

L_{1}

has terminal velocity

{\vec{V}}_{Q}

, then

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

The stream of a river is flowing with a speed of

2 k m h^{- 1}

. A swimmer can swim at a speed of

4 km h^{- 1}

. The direction of the swimmer with respect to the flow of the river, to cross the river straight, is

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A block of mass

10 kg

is kept on a rough inclined plane as shown in the figure. A force of

3 N

is applied on the block. The coefficient of static friction between the plane and the block is

0.6 .

What should be the minimum value of force

P,

such that the block does not move downward? (take

g = 10 m s^{- 2}

)

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

If a machine is lubricated with oil

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Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

A block of mass

2 kg

is placed on the floor. The coefficient of static friction is

0.4

, a force

F

3 N

is applied on the block as shown in the figure. The force of friction between the block and the floor is
(Take

g = 10 m s^{- 2}

)

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Two bodies

A

and

B

of masses

5 kg

and

10 kg

in contact with each other rest on a table against a rigid wall (Fig.

5.21

). The coefficient of friction between the bodies and the table is

0.15 .

A force of

200 N

is applied horizontally to

A

. What are the reaction of the partition?

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A 100 N force acts horizontally on a block of 10 kg placed on a horizontal rough surface of coefficient of friction

μ = 0.5

. If the acceleration due to gravity (g) is taken as 10 m/s², the acceleration of the block (in m/s²) is

HARD

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

A sphere of mass

200 g

is attached to an inextensible string of length

130 cm

whose upper end is fixed to the ceiling. The sphere is made to describe a horizontal circle of radius

50 cm

. Calculate the periodic time of this conical pendulum and the tension in the string.

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A block of mass

m

is moving on a rough horizontal surface, where coefficient of friction between block and surface is

μ = 0 .5

. At

t = 0

, block is moving with a velocity

\vec{v}

, then a horizontal force

F = 2 t

is applied on it in the direction of velocity. Here,

t

represent time, then the speed of block after the application of force

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Two bodies

A

and

B

of masses

5 kg

and

10 kg

in contact with each other rest on a table against a rigid wall (Fig.

5.21

). The coefficient of friction between the bodies and the table is

0.15

. A force of

200 N

is applied horizontally to

A

. What happens when the wall is removed? Does the answer to (b) change, when the bodies are in motion? Ignore the difference between

μ_{s}

and

μ_{k}

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A variable force

F = 25 t

acts on a body of mass

10 kg

kept on a rough horizontal surface

(μ_{s} = 0.6, μ_{k} = 0.4)

. The velocity of the body at

t = 4 s

is,

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A block of mass $5 kg$ , resting on a horizontal surface, is connected by a cord, passing over a light frictionless pulley to a hanging block of mass $5 kg$ . The coefficient of kinetic friction between the block and the surface is $0.5$ . Tension in the cord is [Take $g = 9.8 m s^{- 2}$ ]

Question Image

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

A block of mass

15 kg

is placed on a long trolley. The coefficient of static friction between the block and the trolley is

0.18

. The trolley accelerates from rest with

0.5 {ms}^{- 2}

for

20 s

and then moves with uniform velocity. Discuss the motion of the block as viewed by a stationary observer on the ground.

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

μ_{k}

is the coefficient of kinetic friction,

μ_{r}

the coefficient of rolling friction and

μ_{s}

the coefficient of static friction, then

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A student pulls a wooden box along a rough horizontal floor (without the block loosing contact with the floor) at constant speed by means of a force

P

as shown to the right. (

W

is weight of block,

N

is normal reaction on the block,

f

is force of friction on the block). Which of the following must be true?
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EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

Figure shows a man standing stationary concerning a horizontal conveyor a belt that is accelerating with $1 m s^{-2}$ . What is the net force on the man? If the coefficient of static friction between the man’s shoes and the belt is $0.2$ , up to what acceleration of the belt can the man continue to be stationary relative to the belt?

(Mass of the man $= 65 kg$ .)
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Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

A block of mass 2 kg is placed on the floor. The coefficient of static friction is 0.4. If a force of 2.8 N is applied on the block parallel to floor, the force of friction between the block and floor (Taking

g = 10 m s^{- 2}

) is

EASY

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Starting from rest, the time taken by a body sliding down on a rough inclined plane at

45 °

with the horizontal is twice the time taken to travel on a smooth plane of same inclination and same distance. Then the coefficient of kinetic friction is

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The rear side of a truck is open, and a box of

40 kg

mass is placed

5 m

away from the open end, as shown in Fig.

5.22

. The coefficient of friction between the box and the surface below it is

0.15

. On a straight road, the truck starts from rest and accelerates with

2 m s^{-2}

. At what distance from the starting point, does the box fall off the truck? (Ignore the size of the box and take

g = 10 m s^{- 2}

)

EASY

Physics>Mechanical Properties of Matter>Mechanical Properties of Fluids>Mechanical Properties of Fluids

Match the following.

Table - 1	Table - 2
$(A)$ Force of friction	$(P)$ Opposes motion
$(B)$ Normal reaction on a block kept on horizontal ground	$(Q)$ Opposes relative motion
	$(R)$ Is always $m g$
	$(S)$ May be equal to $m g$
	$(T)$ None

What is a significant impact of droughts on agriculture in India?

Important Questions on Mechanical Properties of Fluids

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