Grade 8 Friction

What kind of friction does the wheel on a skateboard experience?

• Rolling friction

• Fluid friction

• static friction

• Drag

How does friction affect speed?

• More friction increases speed

• More friction decreases speed

• Less friction decreases speed

• Friction has no relation to speed

Assertion (A): Lubricants reduce friction.

Reasoning (R): It forms a thin layer on the moving parts of the machine and moving surfaces do not directly rub against each other.

• Both A and R are true and R is the correct explanation of A

• Both A and R are true but R is not the correct explanation of A

• A is true but R is false

• A is false but R is true

Assertion (A): Gymnasts often apply coarse substances /chalk on their hands to have better grip of uneven bars.

Reasoning (R): The chalk powder increases friction between their hands and the uneven bars.

• Both A and R are true and R is the correct explanation of A

• Both A and R are true but R is not the correct explanation of A

• A is true but R is false

• A is false but R is true

Assertion (A): We do not slip when we walk on wet floor.

Reasoning (R): The water forms thin layer between the feet and the floor and decreases the friction.

• Both A and R are true and R is the correct explanation of A

• Both A and R are true but R is not the correct explanation of A

• A is true but R is false

• A is false but R is true

It is difficult to walk on an oily floor because _______________

• force of friction is very less

• force of friction is very high

• it can cause accidents

• pressure is very low

Lubricants are substances that _______________

• increase friction

• decrease friction

• May increase or decrease friction depending upon its characteristics

• none of them

In which of the following scenarios will you experience maximum friction?

• smooth object over smooth surface

• smooth object over rough surface

• rough object over smooth surface

• rough object over rough surface

What type of friction is it when the object does not move even when external force is applied on it?

• solid

• static

• dynamic

• sliding

Friction is a force that acts ___________ to the direction of motion.

• similar

• parallel

• normal

• opposite