NCERT Solution for Class 8 Science : Friction
Discussed NCERT Solution for class 8 subject science chapter 12 friction related questions answers of CBSE board.
NCERT Text Book Solution page 155
Question 1:
Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces.
(c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.
Answer 1:
(a) Friction opposes the motion between the surfaces in contact with each other.
(b) Friction depends on the roughness of surfaces.
(c) Friction produces heat.
(d) Sprinkling of powder on the carrom board reduce friction.
(e) Sliding friction is lesser than the static friction.
Question 2:
Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement.
(a) Rolling, static, sliding
(b) Rolling, sliding, static
(c) Static, sliding, rolling
(d) Sliding, static, rolling
Answer 2:
(c) S
tatic, sliding, rolling
Question 3:
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:
(a) Wet marble floor, dry marble floor, newspaper and towel.
(b) Newspaper, towel, dry marble floor, wet marble floor.
(c) Towel, newspaper, dry marble floor, wet marble floor.
(d) Wet marble floor,
dry marble floor, towel, newspaper
Answer 3:
(a) Wet marble floor, dry marble floor, newspaper and towel.
Question 4:
Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Answer 4:
Friction force acts opposite to the motion of the book.
Question 5:
You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer 5:
It become difficult to walk on the floor.
This is because Soapy water fills the irregular space present on floor and make it smoother. As a result, friction become laser. So our feet do not make necessary grip with the floor surface. Hence it is difficult to walk on the floor.
Question 6:
Explain why sportsmen use shoes with spikes.
Answer 6:
Friction increases when surface become more rough. Shoes with spikes has more rough surface henc cellse also has greater friction and can work easily without sleeping. Spike also provide better grief with the ground.So, sportsman use shoes with Spikes to avoid sleeping while playing or running.
Question 7:
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer 7:
Seema has to apply larger force.
Because friction is directly proportional to mass that is if Mars is greater than frictional force is also greater. Since Seema push a heavier box show she face greater fictional force hence she required more force.
Question 8:
Explain why the sliding friction is less than the static friction.
Answer 8:
When the objects are at rest, the interlocking of irregularities in the two surfaces of the objects is higher than that of when objects are moving. When objects are moving, there is less interaction between their surfaces. That's why sliding friction is less than static friction.
Question 9:
Give examples to show that friction is both a friend and a foe.
Answer 9:
In one side fiction help us in our daily life such as for walking, for holding objects, nails can fixed to wall, we can write on paper. Again friction also harmful to us such as wear and tears occurs, machine parts get heated, machine consume more fuel, wear and tears occur on tyres, roads, shoe soles due to friction. Hence, fiction act as a friend as well as foe.
Question 10:
Explain why objects moving in fluids must have special shapes.
Answer 10:
When a body moving in fluids it faces frictional force provided by fluid which is termed as drag. To overcome this drag the floating body needs special shape. Streamlined body is the special safe which minimise this drag.
NCERT Text Book Solution page 155
Question 1:
Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces.
(c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.
Answer 1:
(a) Friction opposes the motion between the surfaces in contact with each other.
(b) Friction depends on the roughness of surfaces.
(c) Friction produces heat.
(d) Sprinkling of powder on the carrom board reduce friction.
(e) Sliding friction is lesser than the static friction.
Question 2:
Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement.
(a) Rolling, static, sliding
(b) Rolling, sliding, static
(c) Static, sliding, rolling
(d) Sliding, static, rolling
Answer 2:
(c) S
tatic, sliding, rolling
Question 3:
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:
(a) Wet marble floor, dry marble floor, newspaper and towel.
(b) Newspaper, towel, dry marble floor, wet marble floor.
(c) Towel, newspaper, dry marble floor, wet marble floor.
(d) Wet marble floor,
Answer 3:
(a) Wet marble floor, dry marble floor, newspaper and towel.
Question 4:
Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Answer 4:
Friction force acts opposite to the motion of the book.
Question 5:
You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer 5:
It become difficult to walk on the floor.
This is because Soapy water fills the irregular space present on floor and make it smoother. As a result, friction become laser. So our feet do not make necessary grip with the floor surface. Hence it is difficult to walk on the floor.
Question 6:
Explain why sportsmen use shoes with spikes.
Answer 6:
Friction increases when surface become more rough. Shoes with spikes has more rough surface henc cellse also has greater friction and can work easily without sleeping. Spike also provide better grief with the ground.So, sportsman use shoes with Spikes to avoid sleeping while playing or running.
Question 7:
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer 7:
Seema has to apply larger force.
Because friction is directly proportional to mass that is if Mars is greater than frictional force is also greater. Since Seema push a heavier box show she face greater fictional force hence she required more force.
Question 8:
Explain why the sliding friction is less than the static friction.
Answer 8:
When the objects are at rest, the interlocking of irregularities in the two surfaces of the objects is higher than that of when objects are moving. When objects are moving, there is less interaction between their surfaces. That's why sliding friction is less than static friction.
Question 9:
Give examples to show that friction is both a friend and a foe.
Answer 9:
In one side fiction help us in our daily life such as for walking, for holding objects, nails can fixed to wall, we can write on paper. Again friction also harmful to us such as wear and tears occurs, machine parts get heated, machine consume more fuel, wear and tears occur on tyres, roads, shoe soles due to friction. Hence, fiction act as a friend as well as foe.
Question 10:
Explain why objects moving in fluids must have special shapes.
Answer 10:
When a body moving in fluids it faces frictional force provided by fluid which is termed as drag. To overcome this drag the floating body needs special shape. Streamlined body is the special safe which minimise this drag.
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NCERT Solution for Class 8 Science : Friction
