FRICTION CLASS 8

The force of friction always

• Opposes motion

• Helps the motion

• Both of these

• None of the above

Answer explanation

It is because the frictional force always acts in the direction opposite to the direction of motion of a body

Friction is due to

• Polishing of surface

• Streamlining of body

• Interlocking of irregularities

• None of the above

Whenever the surfaces in contact tend to move with respect to each other , the force of friction comes into play

• only if one of the two objects is liquid

• only if the objects are solid

• only if one of the two objects is gas

• Irrespective of whether the objects are solid,liquid or gas.

It is difficult to walk on the wall polished floor because friction between our feet and floor is

• Increased

• Reduced

• Same

• None of these

In Fig., a boy is shown pushing the box from right to left. The force of friction will act on the box

• (a) from right to left (←)

• (b) from left to right (→)

• (c) vertically downwards (↓)

• (d) vertically upwards (↑)

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

• stone

• plastic block

• wooden block

• glass block

Answer explanation

Stone will be more suitable because it will exert greater reaction and hence greater friction force in comparison of other surfaces.

A toy car released with the same initial speed will travel farthest on

• Muddy surface

• polished marble surface

• cement surface

• brick surface

We can increase the friction by

• Polishing

• Making grooves and treads

• Streamlining

• Using ball bearing

We can apply oil on door hinges, the friction will

• Increase

• Decrease

• Disappear altogether

• Will remain unchanged

Fine powder is poured on the carrom board to

• A. Increase friction

• B. Decrease friction

• C. Both a and b

• D. None of these