1. A 8 kg block is at rest on a horizontal floor. If you push horizontally on the 8 kg block with a force of 20 N, it just starts to move.
(a) What is the coefficient of static friction?
(b) A 10.0 kg block is stacked on top of the 8 kg block. What is the magnitude F of the force, acting horizontally on the 8 kg block as before, that is required to make the two blocks start to move?
2. A box sits on a horizontal wooden board. The coefficient of static friction between the box and the board is 0.5. You grab one end of the board and lift it up, keeping the other end of the board on the ground. What is the angle between the board and the horizontal direction when the box begins to slide down the board?
-
UP 0 DOWN 0 0 2
2 Answers
311.a)coefficient of static friction = 20/(8*9.8)
=0.25
b) total mass = 18 kg
force requied =0.25 * 18* 9.8
=44.1N
2)let the angle be x
then tan x = coefficient of static friction
= 0.5
then x =26 degree 34 minute
