Learn Science Friction , Class 8 Science Friction Exercise, Free Online Friction Lessons

Class 8 Science Study Material

An Educational platform for Preparation and Practice Class 8. Kidsfront provide unique pattern of learning Science with free online comprehensive study material in the form of QUESTION & ANSWER for each Chapter of Science for Class 8. This study material help Class 8, Science students in learning every aspect of Friction . Students can understand Friction concept easily and consolidate their learning by doing Online Practice Tests on Science, Friction chapter repeatedly till they excel in Class 8, Friction . Free ONLINE PRACTICE TESTS on Class 8, Friction comprise of Hundreds of Questions on Friction , prepared by the highly professionals team. Every repeat test of Friction will have new set of questions and help students to prepare themselves for exams by doing unlimited Online Test exercise on Friction . Attempt ONLINE TEST on Class 8,Science, Friction in Academics section after completing this Friction Question Answer Exercise.

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Friction

To reduce friction in some machines between the moving parts, the device used is

a) Solid cushions.
b) Air cushions.
c) Fibre glass.
d) Paper cushions.

✔Answer

✔Solution

Correct Answer Is : Air cushions.

Solution Is : In some machines, it is not advisable to use oil as lubricant. So, air cushions are used between the moving parts to reduce friction.

Friction between the road and grooves of car tyres allows

a) Safe driving.
b) Unsafe driving.
c) Difficult driving.
d) Easy driving.

✔Answer

✔Solution

Correct Answer Is : Safe driving.

Solution Is : Friction is the opposing force which acts between two surfaces in contact. So, if without friction between the road and the surface of the tyres, the vehicle might skid, resulting in an accident.

The heat generated when a machine is operated, causes a wastage of

a) Time.
b) Money.
c) Energy.
d) Material.

✔Answer

✔Solution

Correct Answer Is : Energy.

Solution Is : Friction can produce heat. When a machine is operated, this heat generated causes a lot of wastage of energy. Then ways have to be adopted to minimise friction.

To start to slide a heavy box across the floor is harder than to keep it sliding because

a) Static friction is greater than kinetic friction.
b) Kinetic friction is greater than the static friction.
c) Sliding friction is less than rolling friction.
d) It needs more force to overcome sliding friction.

✔Answer

✔Solution

Correct Answer Is : Static friction is greater than kinetic friction.

Solution Is : In order to start sliding a heavy box, we have to overcome first the static friction i.e., we have to apply force to remove the box`s contact points locked with those of the floor. The force required in this case is more than that required while the box is in motion.

An advantage of using rollers instead of sliding an object is that

a) Rollers are less expensive.
b) Rolling friction is less than sliding friction.
c) Rolling friction is more than sliding friction.
d) Rollers are easy to handle.

✔Answer

✔Solution

Correct Answer Is : Rolling friction is less than sliding friction.

Solution Is : The area of contact while rolling is much less as compared to that in case of sliding. So, rolling friction is less than sliding friction.

To increase the friction of a muddy ground, it is sprinkled with

a) Oil.
b) Sand and gravel.
c) Grease.
d) Talcum powder.

✔Answer

✔Solution

Correct Answer Is : Sand and gravel.

Solution Is : When sand and gravel is sprinkled on a muddy ground, the surface becomes rough. The force of friction is greater on a rough surface.

In absence of an external force, a moving object after sometime comes to a stop on its own due to

a) Its velocity.
b) Friction.
c) Magnetic force.
d) The smoothness of the surfaces.

✔Answer

✔Solution

Correct Answer Is : Friction.

Solution Is : Friction occurs when two objects are moving relative to each other. It is the force resisting the relative motion of two surfaces. So, a moving body in absence of any external force will come to a stop due to the frictional force.

The use of ball bearings between the hubs and the axles of bicycles is an example of

a) Static friction.
b) Sliding friction.
c) Rolling friction.
d) Fluid friction.

✔Answer

✔Solution

Correct Answer Is : Rolling friction.

Solution Is : The ball bearings between the hubs and axles of bicycles are an application of rolling friction. As rolling friction is smaller than sliding friction, sliding in most machines is replaced by the rolling of ball bearings.

The force of friction increases if the two surfaces are

a) Pressed harder.
b) Pressed smoothly.
c) Left untouched.
d) Just touched.

✔Answer

✔Solution

Correct Answer Is : Pressed harder.

Solution Is : The force of friction will increase if the two surfaces are pressed harder, as the irregularities get locked more tightly. This can be experienced by dragging a mat, in two different conditions, when nobody is sitting on it and then, with a person sitting on it.

If the force is applied along the downward direction, the friction acts

a) Upwards.
b) Downwards.
c) Right hand side.
d) Sideways.

✔Answer

✔Solution

Correct Answer Is : Upwards.

Solution Is : Frictional force always acts in opposite direction to the applied force. So, when a force is applied along the downward direction, frictional force acts along the upward direction.

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Class 8 Science Study Material

Friction

To reduce friction in some machines between the moving parts, the device used is

Correct Answer Is : Air cushions.

Solution Is : In some machines, it is not advisable to use oil as lubricant. So, air cushions are used between the moving parts to reduce friction.

Friction between the road and grooves of car tyres allows

Correct Answer Is : Safe driving.

Solution Is : Friction is the opposing force which acts between two surfaces in contact. So, if without friction between the road and the surface of the tyres, the vehicle might skid, resulting in an accident.

The heat generated when a machine is operated, causes a wastage of

Correct Answer Is : Energy.

Solution Is : Friction can produce heat. When a machine is operated, this heat generated causes a lot of wastage of energy. Then ways have to be adopted to minimise friction.

To start to slide a heavy box across the floor is harder than to keep it sliding because

Correct Answer Is : Static friction is greater than kinetic friction.

Solution Is : In order to start sliding a heavy box, we have to overcome first the static friction i.e., we have to apply force to remove the box`s contact points locked with those of the floor. The force required in this case is more than that required while the box is in motion.

An advantage of using rollers instead of sliding an object is that

Correct Answer Is : Rolling friction is less than sliding friction.

Solution Is : The area of contact while rolling is much less as compared to that in case of sliding. So, rolling friction is less than sliding friction.

To increase the friction of a muddy ground, it is sprinkled with

Correct Answer Is : Sand and gravel.

Solution Is : When sand and gravel is sprinkled on a muddy ground, the surface becomes rough. The force of friction is greater on a rough surface.

In absence of an external force, a moving object after sometime comes to a stop on its own due to

Correct Answer Is : Friction.

Solution Is : Friction occurs when two objects are moving relative to each other. It is the force resisting the relative motion of two surfaces. So, a moving body in absence of any external force will come to a stop due to the frictional force.

The use of ball bearings between the hubs and the axles of bicycles is an example of

Correct Answer Is : Rolling friction.

Solution Is : The ball bearings between the hubs and axles of bicycles are an application of rolling friction. As rolling friction is smaller than sliding friction, sliding in most machines is replaced by the rolling of ball bearings.

The force of friction increases if the two surfaces are

Correct Answer Is : Pressed harder.

Solution Is : The force of friction will increase if the two surfaces are pressed harder, as the irregularities get locked more tightly. This can be experienced by dragging a mat, in two different conditions, when nobody is sitting on it and then, with a person sitting on it.

If the force is applied along the downward direction, the friction acts

Correct Answer Is : Upwards.

Solution Is : Frictional force always acts in opposite direction to the applied force. So, when a force is applied along the downward direction, frictional force acts along the upward direction.

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