CBSE Questions for Class 8 Physics Friction Quiz 5 - MCQExams.com

Friction is not required in which of the following cases?
  • Man running on the ground.
  • Friction between parts of a machine.
  • Writing with a pen.
  • Monkey climbing a tree.
Frictional force is nearly negligible on :
  • Rough surfaces
  • Semi-smooth surfaces
  • Smooth surfaces
  • None of these
The depressions and elevations present on the surface of objects causes friction.
  • True
  • False
Which of the following activity would not be possible in the absence of friciton?
  • holding a glass
  • writing on a paper
  • sitting on a chair
  • all of the above
Friction does not depend on the nature of the surface in contact.
  • True
  • False
Driving a car on a wet road is difficult because water
  • makes it difficult to turn the car.
  • decreases the friction between the tyres and the road.
  • increases the friction between the tyres.
  • makes friction between the road and tyres zero.
If rough surface is polished beyond a certain limit than the magnitude of frictional force will
  • Nothing can be said.
  • sometime increases and sometime decreases.
  • increase.
  • decrease.
From following statements choose the correct combination.
A. Grease is used to reduce friction in bicycle chain
B. Ball bearings are used to reduce friction in a fan
C. Oil can be used to increase friction in a car engine.
D. Talc can be used to reduce friction when an object is sliding on a surface. 
  • A, B, D
  • A, C, D
  • B, C, D
  • A, B, C
The application of decreasing friction includes :
  • Ball bearing used in moving parts of a machine
  • The streamlined shape of an aircraft
  • The layer of air between the hull of a hovecraft.
  • All of the above
The friction of the surface of a wooden bench can be increased by;
  • rubbing it with sand paper.
  • using lubricants like oil and grease.
  • using powder lubricants.
  • grinding or polishing the surface.
What would happen to a moving object if there would be no friction?
  • The object will stop
  • The object will keep moving
  • The object will change speed
  • The object will change direciton
Friction on a dry marble floor is ----- than that on a wet marble floor.
  • More
  • Less
  • Same
  • None of these
Boats and aeroplanes are ................. so as to reduce fluid friction.fill in the blank.
  • large
  • broader
  • streamlined
  • bigger
Air resistance is also a form of friction.
  • True
  • False
Unevenness in the surfaces of the moving body and the surface on which it moves causes:
  • gravitational force
  • frictional force
  • centripetal force
  • centrifugal force
Any substance which is used to reduce the roughness of a surface is called a:
  • Lubricant
  • Lubrant
  • Lubrication
  • None of these
To keep machines running smoothly and to avoid wear and tear of machines, the best and the most commonly used lubricant is:
  • powder
  • sand
  • oil
  • water
Graphite powder is used in machines to
  • Enhance friction
  • Enhance profit
  • Reduce friction
  • Reduce efficiency
A car will skid more on a wet road than on a dry road and the car tyres there is more:
  • friction
  • lubricant
  • gravity
  • heat
Friction between any two objects is due to
  • attraction between them
  • repulsion between them
  • some adhesive forces between them
  • irregularities on the surfaces
Frictional force increases when surfaces in contact are made very smooth, because of 
  • Molecular force
  • Decrease in surface area
  • Decrease in irregularities
  • Increase in area
Match the following
List IList II
1Streamlined body structureaLess no. of irregularities
2Pressing two objects harder against each otherbLubricant
3GreasecIncrease friction
4Smooth surfacedDecrease friction
  • 1-d, 2-c, 3-b, 4-a
  • 1-d, 2-c, 3-a, 4-b
  • 1-a, 2-d, 3-b, 4-c
  • 1-a, 2-b, 3-c, 4-d
Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
  • Wet marble floor, dry marble floor, newspaper and towel.
  • Newspaper, towel, dry marble floor, wet marble floor.
  • Towel, newspaper, dry marble floor, wet marble floor.
  • Wet marble floor, dry marble floor, towel, newspaper.
After an aeroplane completes a voyage, its muzzle feels warmer than the middle and back portion of the main body. This is because:
  • the muzzle tears apart the air layers and suffers more air friction
  • the muzzle suffers less air friction
  • the muzzle suffers zero air friction
  • none of these
A ball is rolled on four surfaces:
a) marble floor,  
b) on sand,  
c) on cloth, 
d) on wood.
The force of friction acting on the ball on these different surfaces in descending order will be:
  • b > c > d > a
  • c > b > d > a
  • d > b > a > c
  • a > b > c > d
If we drop a cup of water on a plate and a cup of oil on another plate, water is seen to spread faster along diameter. This is an example related to:
  • fluid friction
  • rolling friction
  • sliding friction
  • static friction
What measures are taken to reduce fluid friction in aeroplanes?
  • Optimum speed is maintained with respect to the air
  • Metals are choosen in a way to make the aeroplane lighter with smoother surface
  • Streamlined body inspired by birds
  • All of the above
Why are efforts made to reduce friction?
  • Energy is lost in overcoming friction.
  • Overcoming friction is a time consuming process.
  • Both A and B
  • None of the above
When two surfaces are coated with lubricant, then they will:
  • slide upon each other
  • stick to each other
  • roll upon each other
  • jump on each other
Aeroplanes are streamlined to reduce friction.
  • True
  • False
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