Class 8 Basic Science (English Medium) Chapter 10 Force - Questions and Answers
Textbooks Solution for Class 8th Basic Science (English Medium) | Text Books Solution Physics (English Medium) Chapter 10 Force

 
Class 8 Physics - Questions and Answers 
Chapter: 10 - Force
1. Force is a physical quantity that can make a change in shape, size, volume and state of motion of an object.
a. What is the unit of force?  
b. Give two examples each for contact force and non-contact force.
c. What is frictional force?    
d. Which is the force that exists in between all the objects in the universe?
Ans.
a. newton. 
b. Contact forces: muscular force, frictional force.
Non-contact forces: Magnetic force, Gravitational force.
c. It is the force that comes into play when an object moves or tends to move over another object.
d. Gravitational force. 

2. It is due to frictional force, the speed of a ball rolling on the ground decreases.
a. Rolling an object is easier than sliding. Why?
b. Write down the advantages and disadvantages of friction.
c. Suggest three methods to reduce friction.
Ans. 
a. Because rolling friction is less than sliding friction.
b. Advantages: we can hold things, can walk without slipping, can stop the vehicle by applying the brake.
Disadvantages: causes tear wear of footwear, machine parts etc.., Cause fuel loss.
c. Apply lubricants, polish the surfaces in contact, Streamlining. 

3. By changing the shape of the objects, friction can be reduced.
a. What is called this type of shaping? 
b. What is a lubricant? Give two examples.    c.  ............ is an example of solid lubricant.
Ans.
a. Streamlining.   
b. Substance used to reduce friction is called lubricants., Examples. Oil, grease.
c. Graphite. 

4. Match the columns A, B and C appropriately.

 A

 B

 C

 Pressure

 Lubricant

 Mg

 Weight

 N/m2

 Graphite

 Friction

 Gravitational force

 Pascal
Ans.

 A

 B

 C

 Pressure

 N/m2

 Pascal

 Weight

 Gravitational force

 Mg

 Friction

 Lubricant 

 Graphite

5. In our daily life, we have to face situations where friction is to be reduced.
a. Identify the substance shown in the figure.
b. Which feature of friction is made in the use of this? 
Ans. 
a. Bearing.
b. Rolling friction is less than sliding friction.

6. match the columns A, B suitably
7. Placed three identical bricks on the sand in a tray in different ways.
a. Find out the situation at which area of contact is maximum.
b. Where the thrust is maximum?
c. What is the relation between pressure and area of contact?
Ans. 
a. Fig.C       
b. Thrust is same in all the three.   
c. The pressure decreases with the increase in area.

8. Force per unit area is called pressure.
a.Write down the equation for calculating pressure.
b. What is the unit of pressure? 
c. Cite an example of a situation where the area is reduced to increase pressure.
d.The strap of travel bags is made wide. Why? 
Ans.
a. Pressure P =  Thrust/Area
b. N/m (pascal )       
c. Edge of knives makes thin.
d. When the strap is wide, its area of contact increases. Hence pressure experienced on our body due to its weight decreases.
9. Which of the following conditions in which atmospheric pressure applies.
a. Drinking Juice using a straw
b. Attraction of nail by a magnet
c. filling ink Using a filler
d. paper bits get attracted to a glass rod which is well rubbed with silk
Ans.
a. Drinking Juice using a straw
c. filling ink Using a filler 

10. It is seen a person is lying safely on a nail bed.
a. What is the science of this?
b. Give an example where this principle is made in use? 
Ans.
a. Pressure decreases when the area of contact increases.
b. Wide wheels are used in goods vehicles. 

11. The weight of the air column over the unit area of the earth's surface is atmospheric pressure.
a. What is the unit of atmospheric pressure?
b. Atmospheric pressure ..... as we go up. ( increases/ decreases)
c. Name the device used to measure atmospheric pressure.  
Ans.
a. bar         b. decreases.     c. Barometer

12. Three identical balloons are fixed on a PVC pipe as shown.
a. If water is filled in the pipe, which balloon will swell up more? Justify your
answer.
b. What are the factors influencing liquid pressure.
c.Write down the equation for liquid pressure.
Ans.
a. As liquid pressure increases with depth (height of liquid column), the lowermost balloon will swell up more.
b.Height of liquid column (h), Density of liquid (d), Acceleration due to gravity(g)  c. Liquid pressure P = hdg.

13. Find out the reason for the following.
a. The number of tyres is more for goods vehicles.
b. Sharp nails can be nailed easily.
c. There is a possibility of nasal bleeding when mountaineers climb higher.
d. It is able to walk on the ground without slipping.
Ans.
a. Pressure decreases when the area of contact increases.
b. When the nail is sharp, the area of contact decreases. Hence high pressure is made available while hammering.
c. Atmospheric pressure decreases with an increase of altitude.
d. Due to the frictional force between the foot and the floor. 

14. The raising of bubbles from the bottom of water-filled bottles are shown in the figures.   
a. Find out the correct figure. Justify.
b. What is the relation between pressure and density?
Ans.
a.  The figure (c) is correct. Because pressure is high at the bottom bed. 
b. Pressure increases with an increase in density.

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