Force and Pressure Test

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Force and Pressure Test - 43

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Question 1
1 / -0

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

A
Acceleration

B
Force

C
Energy

D
None

Solution

Newton's first law of motion states that a body can change its state of rest or of uniform motion only when acted upon by some external force.
Question 2
1 / -0

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?

A

B

C

D
Cannot be said

Solution

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.
Question 3
1 / -0

A tall vertical cylinder filled with water is kept on a horizontal table top. Two small holes A and B are made on the wall of the cylinder, A near the middle and B just below the free surface of water.

A
Water jet through A will have larger range

B
Water jet through B will have larger range

C
Water jets through A and B will have equal range

D
There will be no water jet through B

Solution

The water jet through A will have larger horizontal range because water pressure is more at that point. While B is just below the surface so water will come out of it without any significant pressure or jet. It will just leak through it.
Question 4
1 / -0

At sea-level, atmospheric pressure is

A
$$\;76\;cm\;of\;Hg$$ column

B
$$\;0.76\;cm\;of\;Hg$$ column

C
$$\;76\;m\;of\;Hg$$ column

D
$$\;76\;cm\;of\;water$$ column

Solution

At sea -level , atmospheric pressure is equal to $$76cm$$ of $$Hg$$(MERCURY) column.That is , at sea -level , atmospheric pressure is equal to pressure due to weight of $$76cm$$ height of $$Hg$$ column per unit area.
Question 5
1 / -0

The pressure exerted by a force of $$50 \ N$$, normal to the nail of area $$1 \ mm^2$$ is

A
$$5 \times 10^7$$ Pa

B
$$5 \times 10^6$$ Pa

C
$$5 \times 10^5$$ Pa

D
$$5 \times 10^4$$ Pa

Solution

Given:
Force $$F=50 \ N$$
Area $$A= 1 \ mm^2=(10^{-3} \ m) \times (10^{-3} \ m)=10^{-6} \ m^2 $$

We know that,
Pressure $$P=\dfrac{F}{A}=\dfrac{50}{10^{-6}}=5 \times 10^7 \ N/m^2$$
Also, $$1 \ N/m^2= 1 \ Pa$$
So pressure $$P=5 \times 10^7 \ Pa$$

Answer: $$(A)$$
Question 6
1 / -0

Two forces $$F_{1}$$ and $$F_{2}$$ are acting on a body. $$F_{1}$$ is a contact force. $$F_{2}$$ is a non - contact force. Then, the body (if at all moving) always moves in direction of

A
$$F_{1}$$

B
Force whose magnitude is greater

C
$$F_{2}$$

D
None of the above

Solution
Question 7
1 / -0

Which of the following statement is incorrect:

A
At high altitude air pressure is relatively low.

B
At high altitude density of air is relatively high

C
Density of a gas is directly proportional to its pressure at constant temperature.

D
Air is compressible at constant temperature

Solution
Question 8
1 / -0

The U-tube acts as a water siphon. The bend in the tube is lm above the water surface. The tube outlet is 7m below the water surface. The water issues from the bottom of the siphon as a free jet at atmospheric pressure. Determine the speed of the free jet and the minimum absolute pressure of the water in the bend. Given atm pressure $$=1.01\times 10^5 \,N / m^2.g =9.8m /s^2, p_w =10^3\, kg/g/m^3) $$

A
$$10 \, m/s, 2\times 10^4 \, N/m^2$$

B
$$11.7 \, m/s, 2.27\times 10^4 \, N/m^2$$

C
$$5 \, m/s, 4\times 10^4 \, N/m^2$$

D
$$12 \, m/s, 3\times 10^4 \, N/m^2$$

Solution
Question 9
1 / -0

It is recommended that the air pressure in motor car tyres be reduced for a motion of the motor cars on sand because

A
inflated tyres cause high pressure on the sand

B
deflated tyres cause high pressure on the sand

C
inflated tyres cause low pressure on the sand

D
deflated tyres cause low pressure on the sand

Solution
Question 10
1 / -0

The ratio of forces exerted by the larger piston to the smaller piston is

A
1 : 144

B
1 : 72

C
144 : 1

D
72 : 1

Solution