ICSE Living Science Physics for Class 6 Solutions Chapter 4 Friction
Check Your Progress 1 (Page 45)
Fill in the blanks.
Question 1.
More the roughness of a surface, greater is the ……………
Answer:
More the roughness of a surface, greater is the friction.
Question 2.
Rolling friction offers ………….. resistance than sliding friction.
Answer:
Rolling friction offers less resistance than sliding friction.
Question 3.
Weight remaining the same, friction is independent of …………… of surface in contact.
Answer:
Weight remaining the same, friction is independent bf area of surface in contact.
Question 4.
The force of friction acting between two bodies in contact while at rest is known as ………….. friction.
Answer:
The force of friction acting between two bodies in contact
A. Tick the most appropriate answer.
Question 1.
Force of friction comes into play when a/an –
a. object attempts motion
b. moving object tries to stop
c. object is at rest
d. all of the these
Answer:
d. all of the these
Question 2.
Friction always –
a. supports motion
b. starts motion
c. encourages motion
d. opposes motion
Answer:
d. opposes motion
Question 3.
Friction is offered by –
a. solids
b. liquids
c. gases
d. all of these
Answer:
d. all of these
Question 4.
A car skids on a wet or muddy road due to –
a. increased friction between the road and the tyres.
b. lubrication of brakes on a wet road.
c. reduced friction between the road and the tyres.
d. streamlined shape of the car
Answer:
c. reduced friction between the road and the tyres.
Question 5.
Friction for an object can be reduced by
a. providing wheels
b. lubricating
c. streamlining
d. all of these
Answer:
d. all.-of these
Question 6.
Friction produces
a. heat
b. change of state
c. electricity
d. pressure
Answer:
a. heat
Question 7.
If you pour some oil onto a floor, the friction would
a. increase
b. decrease
c. remain the same
d. none of these
Answer:
b. decrease
B. Fill in the blanks.
Question 1.
Rolling friction is …………… than sliding friction.
Answer:
Rolling friction is less than sliding friction.
Question 2.
Smoother the surface, ………….. is the frictional force offered by it.
Answer:
Smoother the surface, lesser is the frictional force offered by it. .
Question 3.
Friction depends upon the …………. of an object.
Answer:
Friction depends upon the weight of an object.
Question 4.
Friction is a type of …………..
Answer:
Friction is a type of contact force.
Question 5.
Bicycles use ………….. to reduce friction between the pedals and the crank.
Answer:
Bicycles use ball bearings to reduce friction between the pedals and the crank.
C. State if the following statements are true or false. Correct the statement if it is false.
Question 1.
Friction wears down the parts of machines.
Answer:
True
Question 2.
Friction has no relation with our walking or running.
Answer:
False. Friction helps us with our walking or running.
Question 3.
Friction helps us to grip the objects in our hand.
Answer:
True
Question 4.
Tyres of vehicles are provided with grooved designs to decrease friction.
Answer:
False. Tyres of vehicles are provided with grooved designs to increase friction.
Question 5.
Friction is offered by all the three states of matter.
Answer:
True
D. Match the following.
| Column A | Column B |
| 1. Rolling friction | a. making grooved designs |
| 2. Static friction | b. regular oiling |
| 3. Reducing friction | c. a book placed on a table top |
| 4. Increasing friction | d. wheels of a car |
Answer:
| Column A | Column B |
| 1. Rolling friction | d. wheels of a car |
| 2. Static friction | c. a book placed on a table top |
| 3. Reducing friction | b. regular oiling |
| 4. Increasing friction | a. making grooved designs |
E. Answer the following in a word or two or in a sentence.
Question 1.
A child tries to slide a wooden block on the top of a table, but she is unable to get a smooth movement. What material do you suggest she should use in between the block and the table to get a smooth movement ?
Answer:
Can use pencils as rollers under the wooden block.
Question 2.
Why is difficult for a pen to leave a mark on a highly smooth plastic sheet ?
Answer:
Because smooth surface has very less friction.
Question 3.
Name the force responsible for opposing the motion between two bodies in contact.
Answer:
Frictional force (friction)
Question 4.
Name a method used to reduce friction.
Answer:
Oiling or lubricating.
F. Answer the following in short.
Question 1.
When you push something heavy, the resistance you feel decreases as soon as the object starts moving. Explain the reason.
Answer:
It is because when the object is at rest, static friction occurs. The static friction is maximum when the applied force is just short of the force required to start motion between the two bodies in contact. Once the object starts moving, friction (resistance) we feel decreases.
Question 2.
Define rolling friction and give an example where rolling friction comes into play.
Answer:
When we roll an object on a surface, the friction produced between the object and the surface is called rolling friction. Example : when we pull our large suitcases on wheels, rolling friction comes into play. The wheels reduce friction and cut down a lot of effort required to move the suitcase (Rolling friction is less than sliding friction).
Question 3.
How can sliding friction be changed into rolling friction easily ?
Answer:
Sliding friction can be changed into rolling friction easily by providing wheels or ball bearings to the objects to reduce friction and facilitate easy movement.
Question 4.
Why do wrestlers rub powder on their hands before getting into the ring ?
Answer:
In order to prevent their hands from slipping over their opponent’s body. The powder increases the friction.
Question 5.
List the various states of matter that offer frictional force.
Answer:
The force of friction is offered by all the three states of matter – solids, liquids and gases.
G. Answer the following in detail.
Question 1.
Define friction and explain how it is useful to us.
Answer:
Friction is a force that opposes relative motion between two bodies/surfaces in contact with each other. Although friction opposes motion, it also makes motion possible. Friction helps us do many things like :
- It helps us in walking. In the absence of friction, we may slip or fall.
- Cars and buses are able to move safely on roads due to the friction between the treaded tyres of these vehicles and the surface of the road.
- Friction allows us to hold objects with our hands.
- It allows us to write on a paper.
- Friction produces heat. In winter, when we rub our cold hands, the heat produced due to friction makes our hands warm.
Question 2.
Write the characteristics of the force of friction.
Answer:
Characteristics of force of friction are :
- Friction opposes the direction of motion.
- It depends on the nature of the surface that are in contact. Rough surfaces offer greater degree of friction as compared to smooth surfaces. More the roughness of a surface, greater is the friction.
- Friction depends upon the weight of the object – greater is the weight of the object, greater is frictional force it faces.
- Friction is independent of area of surface in contact, when the weight remains unchanged.
Question 3.
How is friction harmful to us ? Write some ways by which one can reduce friction.
Answer:
Disadvantages of friction :
- Friction produces heat which damages the moving parts of a machine. ‘
- Friction produces wear and tear on the contacting surfaces. This reduces the life of machine parts, tyres and shoe soles.
- A lot of energy is wasted due to friction to overcome it before moving.
Ways to reduce friction :
- Providing ball bearings or wheels between the moving parts of machine or vehicles reduce friction and allow smooth movement as rolling friction is less than sliding friction.
- Oiling or lubricating (with graphite or grease) the moving parts of a machine reduces friction. Fine powder like talcum powder also works as a lubricant to reduce friction.
- Polishing the rough surface reduces friction offered by it.
- Streamlining (giving special shape to experience minimum drag) the bodies of aeroplanes, cars, boats and ships help reduce drag (fluid friction) while travelling through air or water.
Question 4.
Describe three different ways by which friction can be increased to help us in various situations.
Answer:
Ways by which friction can be increased are :
- Tyres of all vehicles have grooved designs or treads to make their surface rough. Roughness of a surface increases friction and prevents vehicle from slipping or skidding on a wet or muddy road.
- Spikes in the shoe soles used by players and athletes increase friction and they get firm grip on the ground. The soles of footwear are also provided with grooved designs to increase friction and avoid slipping.
- The handles of motorbikes are covered with spiked rubber to provide a good grip and have better control in holding the handies.
H. Give reasons for the following.
Question 1.
Vehicles skid on muddy and wet roads. Suggest what type of tyres can prevent skidding of vehicles.
Answer:
Vehicles slip/skid on muddy and wet roads as the roads become smooth and offer less friction to the tyres. Tyres are therefore grooved or treaded to make their surface rough so that the friction between the tyres and the road increases and vehicles may stop easily when desired.
Question 2.
Boats and ships have streamlined shapes.
Answer:
Streamlined shapes experience minimum drag (fluid friction) while travelling through air and water. Hence, boats and ships are given streamlined shape.
Question 3.
Brake handies of motorcycles are generally covered with a towelled cloth.
Answer:
Rough towelled cloth on the handles of motrbike provides good grip increasing the friction and we have better control in holding the handles.
I. Solve the crossword puzzle.
Across
3. The force of friction caused due to fluids
4. Type of friction acting between two bodies at rest
5. ‘type of friction which occurs when applied force overcomes static friction
6. A special body design to enable minimum drage
Down
1. type of force which depends upon the roughness of a surface
2. An effect of friction
Answer:
Living Science Physics Class 6 ICSE Solutions