Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Assertion is correct but Reason is incorrect

Both Assertion and Reason are incorrect

MCQ Questions for Class 8 Physics Force And Pressure Quiz 10

Atmospheric pressure exerted on earth is due to the.

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Gravitational pull
0%
Revolution of earth
0%
Rotation of earth
0%
Uneven heating of earth

A 50 kg girl wearing heel shoes balances on a single heel. The heel is circular with a diameter 1 cm. The pressure exerted by the heel on the horizontal floor is then (Take g = 10 m s

$^{-2}$ )

0%
6.4 x 10 $^4$ Pa.
0%
6.4 x 10 $^5$ pa
0%
6.4 x 10 $^6$ Pa
0%
6.4 x 10 $^7$ Pa

Explanation

Here,

$m =50 kg,$

$D = 1 cm = 10^{-2} m$ ,

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

$\therefore$ Pressure exerted by the heel on the horizontal floor is

$Pressure=\dfrac{Force}{Area}$ Force here is WEIGHT and area is area of circular portion of heel.

$\displaystyle P=\frac{F}{A} = \frac{mg}{\pi \left(\dfrac{D}{2}\right)^{2}}=\frac{4 mg}{\pi D^2}$

$\displaystyle = \frac{4\times 50 kg \times 10\,m\,s^{-2}}{3.14\times(10^{-2}\,m)^2}=6.4 \times 10^6\,pa$

Force acts on an object may change

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Direction
0%
Speed
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Shape
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All the above

Which of the following pairs of forces will never give resultant force of

$2N$

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$2N$ and $2N$
0%
$1N$ and $1N$
0%
$1N$ and $3N$
0%
None of these

A wooden piece

$5\, N$ in weight and

$5cm \times 3cm \times 2cm$ in size lies on

$5cm \times 2cm$ face. The pressure exerted by it in

$N\, per\, cm^2$ is:

0%
$150$
0%
$50$
0%
$0.5$
0%
$15$

Explanation

force on wooden piece

$=N=mg$

$N=5N$

$P= \dfrac {N}{A} =\dfrac {5N}{10cm^2} =0.5N/cm^2$

The three vessels shown in figure have same base area. Equal volumes of a liquid are poured in the three vessels. The pressure at the base will be

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Maximum in vessel $A$
0%
Maximum in vessel $B$
0%
Maximum in vessel $C$
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Equal in all the vessels

A force acts for 10s on a body of mass ${10^{ - 2}}{\text{kg}}$ initially at rest. Then after the force ceases to act. The body traverses 0.5m in next 5s. The magnitude of the force is

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${10^{ - 1}}N$
0%
${10^{ - 2}}N$
0%
${10^{ - 3}}N$
0%
${10^{ - 4}}N$

Consider two shoulder bags, one with a thin strap, and the other with a wide strap. If both the bags are equally heavy, the bag with the wide strap will be more comfortable to carry because

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the thin strap has greater inertia per unit length
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the thin strap causes greater momentum to be exerted
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the wide strap allows friction to be spread over a bigger area, thus reducing force between shoulder and the strap
0%
the wide strap enables the weight of the bag to be spread over a bigger area, thus reducing the pressure on the shoulder.

Explanation

Pressure is defined as

$P =\dfrac{\text { Force }}{\text { Area }}$

Hence, pressure is inversely proportional to area.

Since, wider strap has more area, than the thinner strap, so less pressure will be applied on shoulder.

Hence, the bag with wider strap is more comfortable.

The correct option is D.

Fill in the blanks.
At least _____________ objects must be present to experience a gravitational force.

0%
1
0%
2
0%
3
0%
4

To move at the same speed, a car with a flat face and another with a streamlined body will require a different amount of force from the engine. The engine of the streamline bodied car will:

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Exert less force
0%
Exert more force
0%
Exert zero force
0%
Exert no force

Write true or false. Correct the false statements.

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The perpendicular distance from the pivot of a rotating body to the line of known as the moment arm.
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pressure is inversely proportional to the force applied
0%
Wooden sleepers are placed under railway tracks in order to increase pres.
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pressure is independent of the roughness of the surfaces in correct.

Three charges

$4q, Q$ and q are in a straight line in the position of

$0, 1/2$ and I respectively. The resultant force on q will be zero, if Q=

0%
- q
0%
$-2q$
0%
$-\frac{q}{2}$
0%
$4q$

A cube of edge length 5 cm is place inside a liquid. The pressure at the center of a face is 12 pa. Find the force exerted by the liquid on this face.

0%
0.03 N
0%
0.08 n
0%
0.06 n
0%
0.3 N

Consider the following two cases which involve the motion of an object
Case 1: An apple falling from a tree towards the ground.
Case 2: To move a loaded cart on the horizontal ground.

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Case 1: Involves pushing of the apple by earth's gravitational force
0%
Case 1: Involves pulling of apple by earth magnetic force
0%
Case 2: Involves loaded cart to be moved by pulling force only
0%
Case 2: Involves loaded cart to be moved by both pulling or pushing force

The force between two charge bodies is called

0%
muscular force
0%
gravitational force
0%
magnetic force
0%
electrostatic force

Explanation

The force between two charge bodies is called electrostatics force.

Hence,

option

$D$ is correct answer.

When three forces of 50N, 30N and 15N act on a body, then the body is

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At rest
0%
Moving with a uniform velocity
0%
In equilibrium
0%
Moving with an acceleration

Explanation

Here all the three force will not keep the particle in equilibrium

$,$

$,$ the net force will not be zero and the part particle will move with an acceleration

$.$

Hence,

option

$(D)$ is correct answer.

Which of the following statements is /are true?

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The strength of a non contact force is independet of distance between the bodies.
0%
Metecors that enter earth atmosphere burn up due to non-contact
0%
Magnet force is a non contact force
0%
Contact forces are always observes than non-contact forcs.

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Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
0%
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
0%
Assertion is correct but Reason is incorrect
0%
Both Assertion and Reason are incorrect

Explanation

since

$P=\rho gh$

the pressure at the bottom of all containers is the same.

now

$F=P\times A$

and it is given that Area A is the same for every container then, the force exerted by the liquid on three vessels is the same.

Hence,

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

A vehicle sinks into soft ground. The vehicle is changed so that it does not sink as far. Which change is made?

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A lower centre of mass
0%
A more powerful engine
0%
Wheels that are further apart
0%
Wider tyres

Explanation

We know that

$Pressure = \dfrac{thrust}{area}$

The weight of vehicle with narrow tyre and the one with wide tyre is the same. That means the thrust is equal in both cases. But we can change the effect of this thrust by changing the area on which it acts. The vehicle sinks into soft ground when the pressure is more, i.e the area is less.

To decrease the pressure, wider tyres must have been used. This increases the area on which thrust acts. So that the vehicle does't sink into the soft ground.

Select the correct alternative:
A force does not change.

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Mass
0%
Length
0%
Shape
0%
State of motion

State if the following statements are true or false. Correct the statement if it is false.
It is possible that a force applied to an object may not bring any change in it.

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True
0%
False

The non-contact force is :

0%
Tension in string
0%
Force of reaction
0%
Force due to gravity
0%
Force of the friction

A force is needed to :

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Change the state of motion or state of rest of the body
0%
Keep the body in motion
0%
Keep the body stationary
0%
Keep the velocity of body constant

Which of the following is a contact force:

0%
Electrostatic force
0%
Gravitational force
0%
Frictional force
0%
Magnetic force

Which of these is an example of a non-contact force?

0%
A toy car slides down the ramp
0%
A bar magnet moves a paperclip without touching it
0%
A child lifts a book lying on the table
0%
A marble rolling on the carpet slows down

Change in the state of rest or of uniform motion is brought about by:

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Acceleration
0%
Force
0%
Energy
0%
None

Anoop places a cuboid of dimensions

$12 cm \times 8 cm \times 6 cm$ with different faces touching the table. Which face touching the table will have the greatest pressure exerted?

0%
0%
0%
0%
Cannot be said

Explanation

Given :- Dimensions of cuboid

$= 12\ cm \times 8\ cm \times 6\ cm$

To find: - from the options, the correct arrangement of cuboid, such that the table will have the greatest pressure exerted.

We know that,

$Pressure = \dfrac {Force}{Area}\Rightarrow P = \dfrac {F}{A}$

$\Rightarrow P\propto \dfrac {1}{A}$

When 'area' of surface which is in contact with the table is less, the pressure exerted will be more.

For option (A)

$Area (A_{1}) = 8\times 12 = 96\ cm^{2}$

For option (B)

$Area (A_{2}) = 6\times 12 = 72\ cm^{2}$

For option (C)

$Area (A_{3}) = 8\times 16 = 48\ cm^{2}$

$A_{1} > A_{2} > A_{3}$

As area

$(A_{3})$ is least among all the areas Pressure exerted by option (C) arrangement will be greatest.

Thus,

Option (C), is the correct choice.

A coin flicked across a table will stop. Why?

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It is heavy.
0%
No force is acting on it.
0%
The Earth attracts the coin.
0%
Table exerts a frictional force.

How could you place an empty bottle on a table so that it produces the greatest amount of pressure on the table?

0%
Position $1$
0%
Position $2$
0%
Position $3$
0%
All positions produce the same pressure.

Explanation

We know,

$Pressure=\dfrac{Force}{Area}$

The empty bottle will exert equal force (weight of the bottle) in all three positions.

$Pressure\propto \dfrac{1}{Area}$

The area of contact is minimum for position

$2$ . Therefore, the empty bottle on the table produces the greatest amount of pressure on the table in position

$2$ .

Figure shows a siphon. The liquid is water. The beakers are open and the points A and B are at the surface of water, exposed to the air. The pressure difference $P_B-P_A$ between the points A and B

0%
$400 Nm^{-2}$
0%
$3000 Nm^{-2}$
0%
$1000 Nm^{-2}$
0%
Zero

Explanation

Points A and B are at the surface of water. Hence, pressure at both points will be equal to the atmospheric pressure.

Hence,

$P_A=P_B=P_{atm}$

$\implies P_B-P_A= 0$

CBSE Questions for Class 8 Physics Force And Pressure Quiz 10 - MCQExams.com

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Practice Class 8 Physics Quiz Questions and Answers

CBSE Questions for Class 8 Physics Force And Pressure Quiz 10 - MCQExams.com

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Practice Class 8 Physics Quiz Questions and Answers

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