Some sliding rocks approach the base of a hill with a speed of 18.0m/s . The hil

Question

Some sliding rocks approach the base of a hill with a speed of 18.0m/s . The hill rises at 39.0? above the horizontal and has coefficients of kinetic and static friction of 0.410 and 0.620, respectively, with these rocks. Start each part of your solution to this problem with a free-body diagram.

a) Find the acceleration of the rocks as they slide up the hill.

b) Once a rock reaches its highest point, will it stay there or slide down the hill?

c) If it slides down, find its acceleration on the way down, else enter 0.

Explanation / Answer

Fnet = m*g*sin39 + uk*m*g*cos39....down the plane

a = Fnet/m = g*(sin39 + uk*cos39).....down the plane

a = 9.29 m/s^2

===========

b) ag = g*sin39 = 6.17

af = us*g*cos39 = 4.72

af < ag

the body will slide

c) Fnet = m*g*sin39 - uk*m*g*cos39

a = Fnet/m = g*(sin39 - uk*cos39)

a = 3.044 m/s^2

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