Science In Everyday Life Solutions for Class 8 Science Chapter 11 Pressure are provided here with simple step-by-step explanations. These solutions for Pressure are extremely popular among class 8 students for Science Pressure Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science In Everyday Life Book of class 8 Science Chapter 11 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science In Everyday Life Solutions. All Science In Everyday Life Solutions for class 8 Science are prepared by experts and are 100% accurate.

Page No 159:

Question 1:

What happens when we try to push an inflated balloon into a bucket of water?

Answer:

When we try to push an inflated balloon into a bucket of water, the water seems to be pushing the balloon upwards due to the pressure that water exerts on the balloon.

Page No 159:

Question 2:

What is atmospheric pressure due to?

Answer:

Atmospheric pressure is the pressure exerted by weight of air above at any point on the earth’s surface.

Page No 159:

Question 3:

Why it is necessary for astronauts to wear pressurized suits?

Answer:

In outer space, the pressure is much lower than atmospheric pressure on Earth. At such low pressures, blood pressure in the blood vessels can lead to bursting open of blood vessels and kill a person. To prevent this and allow themselves to work safely in space, astronauts wear pressure suits.

Page No 159:

Question 1:

Write one word for the following.

1. Force per unit area ....................
2. Liquids and gases together ....................
3. An instrument to measure atmospheric pressure ....................
4. An instrument used to measure pressure ....................

Answer:

  1. Pressure
  2. Fluids
  3. Barometer
  4. Pressure gauge

Page No 159:

Question 2:

Define/Explain the following.
1. Pressure
2. pascal
3. Atmospheric pressure
4. Liquid pressure

Answer:

  1. Pressure is defined as force per unit of area.
  2. Pascal (Pa) is the SI unit of pressure, which is Newton (N) per metre (m2)  i.e. N/m2.
  3. Atmospheric pressure is defined as the pressure exerted on an object by the air above it.
  4. Liquid pressure is the pressure exerted on an object by the liquid in which it is immersed, where a net upward force determines whether the object will sink or float.

Page No 159:

Question 1:

Pressure equals
(a) force/volume
(b) force × area
(c) force/area
(d) force  × volume

Answer:

(c) force/area
Pressure is force per unit area.

Page No 159:

Question 2:

A barometer is an instrument that measures
(a) atmospheric temperature
(b) force
(c) volume
(d) none of these

Answer:

(d) none of these
A barometer is used to measure atmospheric pressure.

Page No 159:

Question 3:

The atmospheric pressure of a place
(a) decreases as altitude decreases
(b) increases as altitude increases
(c) decreases as altitude increases
(d) does not depend on altitude

Answer:

(c) decreases as altitude increases
 Atmospheric pressure decreases as one goes up.

Page No 159:

Question 4:

Rubber suckers stick to a smooth surface because
(a) of a special type of glue
(b) rubber is sticky
(c) a partial vacuum is created and the atmospheric pressure keeps it in place
(d) the smooth surface has no friction

Answer:

(c) a partial vacuum is created and the atmospheric pressure keeps it in place

Rubber suckers can create partial vacuum and they in remain in place because of atmospheric pressure.

Page No 159:

Question 5:

To ensure that skies do not sink into the snow too far, they
(a) should be flat and have a large area
(b) should be slim and have a small area
(c) should be thin and sharp
(d) should have studs

Answer:

(a)should be flat and have a large area

Skies are flat and have a large area to avoid sinking into the snow.

Page No 159:

Question 1:

Match the following.

column A Column B
Pressure Unit of pressure
Liquids and gases Barometer
Atmospheric pressure Force per unit area
pascal Fluids

Answer:

Column A Column B
Pressure Force per unit area
Liquids and gases Fluids
Atmospheric pressure Barometer
pascal Unit of pressure



Page No 160:

Question 4:

What is the effect of altitude on atmospheric pressure?

Answer:

The atmospheric pressure depends on the altitude and decreases as the altitude increases.

Page No 160:

Question 5:

How does liquid pressure vary with depth?

Answer:

Liquid pressure increases with increase in depth.

Page No 160:

Question 6:

Why are dams made stronger and thicker at the bottom than at the top?

Answer:

Liquid pressure increases with increasing depth. To withstand the greater pressure at the bottom of a water reservoir, dams are thicker at the bottom than at the top.

Page No 160:

Question 1:

A force of 25 N acts on an area of 25 cm2. Calculate the pressure produced.

Answer:

Force = 25NArea=25cm2Pressure in Pa = ForceArea in m2We know 1m = 100 cm =102 cmTherefore, 1m2=104 cm2Area in m2 is: 25×10-4m2Therefore, pressure=2525×10-4=104=10000Pa=10kPa

Page No 160:

Question 2:

What is the force needed to produce a pressure of 1 pascal over a square area of side 2 m?

Answer:

Given, pressure =1PaArea of square = 2m×2m=4m2Pressure=ForceAreaForce=Pressure×AreaTherefore,Force = 1×4=4N

Page No 160:

Question 3:

Over what area should a force of 100 N act to produce a pressure of 500 pascal?

Answer:

Pressure=500PaForce = 100 N.Pressure = ForceAreaArea=ForcePressureTherefore, Area=100500=0.2m2

Page No 160:

Question 1:

Explain why a balloon bursts when too much air is blown into it.

Answer:

Being fluids, gases have a property, to exert pressure on bodies immersed in them and on the walls of the container holding them. That is the reason for which a balloon expands when air is blown into it. The air inside the balloon exerts pressure on the inner walls of the balloon. If too much air is blown into the balloon, then the balloon is incapable of withstanding the pressure and it bursts.

Page No 160:

Question 2:

How would you demonstrate the presence of atmospheric pressure?

Answer:

To show the presence of atmospheric pressure, you need a glass tumbler, a stiff cardboard and water. Take the tumbler and fill it with water such that it is full till the brim. Cover it with a cardboard piece. Then place your hand over the cardboard piece on the tumbler and quickly invert it. Now, slowly, remove your hand while supporting the cardboard piece. It is observed that the cardboard piece does not fall. This proves that there is atmospheric pressure that provides enough force to support the weight of the water in the tumbler.

Page No 160:

Question 3:

Explain briefly the construction and working of an open tube manometer.

Answer:


Open tube manometer is a type of simple pressure gauge, an instrument that measures pressure. A manometer is made up of a U-shaped tube containing liquid or sometimes water. One arm of the U-shaped tube is open to the air while the other arm is connected to the vessel in which pressure is being measured. The difference in liquid levels shows the applied pressure. 

Page No 160:

Question 4:

How would you show that liquids exert pressure in all directions?

Answer:

Take a rubber pipe, which is 30 cm in length and a balloon with a mouth that fits tightly onto the pipe. The balloon is taken and without blowing, it is attached to one end of the pipe. Water is filled through one end of the pipe and observed. The tube is then held in a way that the balloon is at different angles, vertical, horizontal and upside down. It is observed that the balloon bulges out due to the pressure of water irrespective of the position of the tube and the angle of the balloon. This proves that water and other liquids exert pressure in all directions.

Page No 160:

Question 5:

Describe any two applications of pressure.

Answer:

Two applications of pressure are

  • Syringes – They are used to draw out blood from vessels during blood tests. Due to the pressure of blood, which is a liquid, it moves into the syringe when the plunger is withdrawn.
  • Vacuum cleaner – It is a machine used for cleaning purposes. It has a fan inside, which creates low pressure inside the machine. This results in the air and dust particles getting sucked into the device. 



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