A 10.0-kg block is at rest on a horizontal floor. If you push horizontally on the 10.0-kg block with a force of 20.0 N, it just starts to move.

(a) What is the coefficient of static friction?

b) A 12.0-kg block is stacked on top of the 10.0-kg block. What is the magnitude F of the force, acting horizontally on the 10.0-kg block as before, that is required to make the two blocks start to move?

1 answer

Fb = 10kg * 9.8 = 98N = Force of block.

Fb = Fv = 98N,

a. Fh - u*Fv = 0,
20 - 98u = 0,
98u = 20,
u = 20 / 98 = 0.20.

b. Fb = (10 + 12)kg * 9.8 = 215.6N.
= Force of blocks.

Fv = Fb = 215.6N.

Fh - u*Fv = 0,
Fh = u*Fv = 0.2 * 215.6 = 43.1N = Force required to move the blocks.