A 15 kg block is on a 10 m long and 8 m high incline. It is attached via a light

Question

A 15 kg block is on a 10 m long and 8 m high incline. It is attached via a light rope that passes
over a light, pulley on a frictionless axis to a 5 kg block which is attached to the top of a spring
with a spring constant of 24 N/m that is initially neither stretched nor compressed. When released
from rest, the 15 kg block starts sliding down the incline. (Use g=10 m/s
2
.)
a) Find the common speed of the two blocks when the 15 kg block has slid 0.5 m down the incline
assuming the incline is frictionless.
b) Repeat part a) assuming the coefficient of kinetic friction between the incline and the 15 kg
block is

Explanation / Answer

a)height reduced =0.5*8/10 =0.4 m
0.5*(15+5)v^2 =15*10*0.4 -0.5*24*0.25
hence v =2.39 m/sec
.
b)if friction is there.. force of friction F= 150cos=18

hence 0.5*20 v^2 =15*10*0.4 -0.5*24*0.25 -18*0.5

v=2.19 m/s

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