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CBSE Questions for Class 8 Physics Friction Quiz 2 - MCQExams.com
CBSE
Class 8 Physics
Friction
Quiz 2
Which of the following is easier to hold with a greasy palm?
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a glass tumbler
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a polished crockery piece
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a metal container
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an earthen pot
Explanation
Option D is correct
The earthen pot is easier to hold because earthen pot is rough, so it has high friction which will prevent it from slipping even at less force.
Which of the following cannot be used as a lubricant?
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grease
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powder
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air
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paper
Explanation
Paper is not used as lubricant due to its roughness and it increases friction.
So it cannot be used as lubricant.
Option D is correct.
Treading of tyres is done to:
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get more mileage
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reduce friction
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increase friction
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drive comfortably
Explanation
The treading of tyres increases the roughness of the surface of the tyre and hence increases the friction.
A ship moving in a sea can't be stopped quickly by applying brakes due to:
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low friction
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excessive friction
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high speed
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none of the above
Explanation
The frictional force exerted by water or any fluid is much less than a solid. Hence it takes more time to stop a ship in water.
$$\therefore$$ Option A is correct.
A streamlined body:
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increases friction
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reduces friction
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decreases weight
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increases weight
Explanation
A streamline body is a shape such that it helps to reduce the friction between a fluid and an object moving through that fluid.
You tend to slip when you accidentally step on a banana peel lying on a smooth surface. This is due
to:
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increased friction
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reduced friction
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gravity
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characteristics of the banana peel
Explanation
The surface of the banana peel is so smooth that it is nearly a frictionless surface whose coefficient of friction is very less, and the frictional force applied is less too. So, when we step on the banana peel, our feet don't stop and slips forward, making us fall.
The force which prevents us from slipping while walking on the road is:
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muscular force of our body
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gravitational pull by earth
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frictional force
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balanced forces of nature
Explanation
When we push the ground with our feet, the friction provides a forward reaction to our push and sends us forward. Walking on smooth ground is difficult because the frictional force is not great enough to prevent slipping.
Option C is correct.
Friction is minimised by using
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Wheels and ball bearings
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More number of tyres in a car
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Rough surfaces
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None of these
Explanation
Answer is A.
Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers 'bear' the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple. Things roll better than they slide. The wheels on our car are like big bearings. If we had something like skis instead of wheels, our car would be a lot more difficult to push down the road.
That is because when things slide, the friction between them causes a force that tends to slow them down. But
if the two surfaces can roll over each other, the friction is greatly reduced.
powder sprinkled on a carrom board
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magnifies friction.
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reduces friction.
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removes friction.
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does not affect friction.
Explanation
The carom board may sometimes be very rough. Sprinkling powder on a microscopic level, the powder particles offer rolling friction to the striker because of which the striker can be used for smooth and fast play.
The surface of a table is smoother as compared to
that of a road. This is due to
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More irregularities on the surface of table
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Less irregularities on the surface of table
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Less irregularltes on the surface of'road
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All of the above
Explanation
Answer is B.
The surface of road has many dips and bumps all along. Also, there are small stone particles are scattered on the road. Whereas, the surface of the table has more or less smooth surface as there are less depressions.
Hence, The surface of a table is smoother as compared to that of a road due to
Less irregularities on the surface of table.
The surface of the head of a matchstick and sides of a match box are deliberately made rough to
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Increase friction
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Decrease friction
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Increase pressure
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Decrease amount of heat
Explanation
Answer is A.
A match is a small stick of wood or strip of cardboard with a solidified mixture of flammable chemicals deposited on one end. When that end is struck on a rough surface, the friction generates enough heat to ignite the chemicals and produce a small flame. Some matches, called strike-anywhere matches, may be ignited by striking them on any rough surface.
Hence, t
he surface of the head of a matchstick and sides of a match box are deliberately made rough to increase friction.
Spikes are provided in the shoes of athlete
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For decoration
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To increase friction
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To decrease friction
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None of the above
Explanation
Answer is B.
Spikes are provided on the soles of shoes of athletes
to increase the friction
between the shoe and the ground.
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
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wet marble floor, dry marble floor, newspaper, towel.
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newspaper,towel, dry marble floor, wet marble floor.
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towel,newspaper, dry marble floor, wet marble floor.
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wet marble floor, dry marble floor, towel, newspaper.
Explanation
Answer is A.
Force of friction depends on the nature of surface in contact. The rougher the surface, the more is the friction between the surfaces in contact and vice-versa. Roughness present in the given surfaces can be arranged in an ascending order as wet marble floor, dry marble floor, newspaper and towel.
Hence, the correct sequence of these surfaces when arranged according to the increase in the force of friction acting on the car is - wet marble floor, dry marble floor, newspaper and towel.
Which of the following material is likely to have least
friction?
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Wood
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Plastic
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Glass
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Paper
Explanation
The glass has least friction in compare to Wood, Plastic and Paper. Because its surface is comparatively smoother and provide less resistance force relative motion.
Hence Option C.
When a bicycle travels on a rough surface, its speed
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increases
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decreases
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remains the same
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none of these
Explanation
When the bicycle moves on the rough surface, its tires experiance some friction force. The direction of friction in front tire always opposes its motion whereas when cylcist stops pandeling, then back tire also opposes its motion due to frection, Hence speed of the bicycle will decrease.
The frictional force direction is ________ to the direction in which the body tends to move relative to the other.
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is always opposite
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is always towards
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sometimes opposite
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sometimes towards
Explanation
The direction of the force of friction is such that it opposes the direction of motion that an object would move if there were no frictional force acting on the object.
The force of friction f is always opposite the direction the object that is moving . If the object would move, then the direction of the force of friction f will be opposite the movement. If the object would not move when there is no friction, then the force of friction is zero.
Hence, the statement is true.
Friction is a/an
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self-adjusting force
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necessary evil
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important force in daily life
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all the above
Explanation
Friction is a force that opposes the relative motion between the surface.
For example,
if you apply the force along the left
on a book lying on a surface
, friction acts along the right. If you apply the force along the right, the friction acts along the left direction. Thus, it is self-adjusting.
It acts equal to the applied force until it reaches its limiting value.
It's a necessary evil. Though it opposes the motion, it helps us to hold things, helps us to walk, and many more things.
It is an important force in daily life. A nail is fixed in the wall due to friction.
So all the options are correct.
Friction between any two objects is primarily due to :
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attraction between them
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repulsion between them
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some adhesive forces between them
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irregularities on the surfaces
Explanation
Friction is caused due to irregularities present on the surface. When we slide an object which has a rough surface over another object which also has a rough surface, the deformities present on the surfaces gets entangled, thus increasing the force required to slide the object over one another. An extra force is required to overcome these irregularities.
Which of the following is used to reduce friction :
1. Streamlines
2. Use of ball bearings
3. Lubrication
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1 & 2 only
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1 & 3 only
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2 & 3 only
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1, 2 & 3
Explanation
All the mentioned option are correct.
Streamlines reduces the friction in fluid.
Use of ball bearing reduces the friction in machines rotating parts.
Lubricants are used in machines and moving parts to reduce friction.
Option D is correct.
_______ is responsible for wear and tear of machine parts.
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Oil
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Steel
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Friction
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Smoothness
Explanation
Friction is responsible for wear and tear of machine parts.
Friction is the main force that is responsible for the wear and tear of machinery, this is why mechanical parts are sometimes oiled, to minimize the friction present.
Friction depends upon ................. of surfaces.
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mass.
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nature of body.
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both A & B
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none
Explanation
Friction depends upon mass and nature of the body of surfaces.
Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. However, friction decreases with smoothness only to a degree; friction actually increases between two extremely smooth surfaces because of increased attractive electrostatic forces between their atoms.
Friction does not depend on the amount of surface area in contact between the moving bodies or (within certain limits) on the relative speed of the bodies. It does, however, depend on the magnitude of the forces holding the bodies together.
When a body is moving over a horizontal surface, it presses down against the surface with a force equal to its weight, i.e., to the pull of gravity upon it; an increase in the weight of the body causes an increase in the amount of resistance offered to the relative motion of all the surfaces in contact.
Friction arises due to the interlocking of hills and .................. present in a body.
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mountain's
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hole's
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valley's
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none
Explanation
Friction arises due to the interlocking of hills and valleys present in a body.
Fill in the blank.
Tyres have treads to _______ friction.
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increase
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decrease
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neglect
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overcome
Explanation
The presence of treads on the tyre increases the roughness of the surface. Because of this increased roughness, the contact between the surface of the tyre and the surface of the road is more prominent. So when the wheel tries to roll on the road, the surface of the road tries to oppose it strongly and hence increases the friction. This friction is useful to prevent the wheel from slipping.
Friction between any two objects is due to
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Attraction between them
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Repulsion between them
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Some adhesive forces between them
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Irregularities on the surfaces
Explanation
Friction between two surfaces is primarily due to the irregularities on the surface. The hills and valleys of one surface interlock with the same of the other surface, this creates restrictive force between two surfaces which restricts relative motion.
A boat is streamlined to reduce the resistance to motion offered by water
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True
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False
Explanation
Streamlined means the shape of the boat is narrow at the front and broader at the back, this is made so as to reduce the surface of the boat that is cutting through the water.
Frictional force always acts in which direction?
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Opposite to that of the object in motion.
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In the same direction as that of the object in motion
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In any direction
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None of the above
Explanation
Frictional force offers the resistance to the applied force opposing its motion. Thus, it always acts in the direction opposite to that of the object in motion. If force is applied to the left, then friction acts in the right.
Fill in the blank.
Force of friction always ____ the applied force.
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Supports
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Opposes
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Extends
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Increases
Explanation
Frictional force acts between two surfaces in contact. It stops the object from moving as the irregularities on both the surface lock into each other, thus obstructing any forward motion. Hence, frictional force always opposes the applied force.
You are marooned on a frictionless horizontal surface and cannot exert any horizontal force by pushing against the surface. How can you get off?
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By jumping
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By spitting or sneezing
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By rolling your body on the surface
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By running on the plane
Explanation
We will need friction to roll or run on any surface. In our case, we have a frictionless surface. Hence, by conservation of linear momentum sneezing can make us move on that surface.
Which of the following forces always acts against the applied force?
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Muscular force
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Mechanical force
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Chemical force
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Frictional force
Explanation
Friction is the force that offers resistance to the relative motion of two surfaces whether solid, liquid or gas against each other. Thus, always acting against the applied force.
Ex: let a force is applied on a block kept on the floor in right direction, the direction of friction always will be towards left.
A ball rolling on the ground stops on its own after some time. Why?
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The ball is stopped by an external force.
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The force of friction acts against the motion of the ball.
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The ball moves only for a set period of time.
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None of the above
Explanation
The force of friction acts between the two surfaces by opposing the relative motion of one surface over the other. For example, when the ball rolls on the ground, the force of friction acts between the surface of the ball and the surface of the ground. The irregularities between the two surfaces lock into each other and thus, stop the ball from moving any further unless it is moved by an external force.
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