Question

1) While walking on ice, one should take small steps to avoid slipping. This is because smaller steps ensure
(a) larger friction (b) smaller friction
(c) larger normal force
(d) smaller normal force
which one is correct??

2) When two surfaces are polished, the friction coefficient between them decreases. But the friction coefficient increases and becomes very large if the surfaces are made highly smooth. Explain.

Answer 1

I think for part 1, both a) and c) are correct. A large frictional force is what you want in order to avoid slipping over, and a large frictional force requires a large normal force since Frictional force=coefficient of friction*Normal force. I don't know about part 2 sorry

Answer 2

Correct answer to 1 is (b) smaller friction.
But I don't know how.

Answer 3

I don't see why the answer is C, surely you want more friction in order to increase the horizontal force between your body and the ice. Maybe @Fifciol knows.

Answer 4

The smaller the steps, the smaller the friction force needed for motion => you stay beyond the friction coefficient for static friction with smaller steps and do not slip.

Answer 5

When you get to questions relative to work/power of (static or kinetic) friction forces, let us know. Even Verma makes mistakes in his concepts there ;-)

Answer 6

I could be wrong but I'll try to answer question 2:
When two surfaces touch each other, only the little areas of the surfaces are really faced, making the contacs. That phenomenon is called the adhesion. See how it looks like:

when you smooth the surface the number of contacs is decreased:

that means smaller frictional force.
But if the surfaces are very very smooth it means that the contacs area is very huge so the frictional force(and so the coefficient) increases vastly.