a) Determine the speed of the rock at point B. b) Determine the energy stored in
ID: 2036422 • Letter: A
Question
a) Determine the speed of the rock at point B.
b) Determine the energy stored in the spring once the rock is at rest and the spring is compressed.
c) Determine the distance "d" between the point B at the bottom of the hill and the beginning of the spring: Note there is still friction underneath the spring.
d) What is the minimum coefficient of static friction if the rock doesn't move while the spring is compressed?
Edit: Time was not given in this question, I typed it exaclty as it was given.
3) An 18.0-kg rock slides down an icy (frictionless) hill 20.0 m tall and 15.0m long. The roc slides across a rough contrete parking lot such that the of kinetic friction is 0.85. Finally t compresses a spring of force constant 9800 N/m a distance of 0.50m and comes to rest (a) Determine the speed of the rock at point B. (b) Determine the energy stored in the spring once the rock is at rest and the spring is (c) Determine the distance "d" between the point B at the bottom of the hill and the begi spring: Note there is still friction underneath the spring. (d) W compressed? co hat is the minimum coeficient of static friction if the rock doesn't move while the 20 m 15 m> RoughExplanation / Answer
mass, m=18kg
height, h=20m
uk=0.85
K=9800 N/m
compression, x=0.5 m
a)
use,
1/2*m*v^2 = m*g*h
1/2*18*v^2=18*9.8*20
===> v=19.8 m/sec
speed at B is, v=19.8 m/sec
b)
energy stored, U=1/2*k*x^2
=1/2*9800*0.5^2
=1225 J
c)
use,
K2-K1=W_friction
1/2*m*v^2-1/2*m*u^2= fk*d
1/2*m*v^2-1/2*k*x^2 = uk*N*d
1/2*m*v^2 - 1225 =uk*m*g*d
1/2*18*19.8^2 - 1225 = 0.85*18*9.8*d
===> d=15.362 m
distannce between the point B and the begining of the spring, d=15.362
d)
use,
K2-K1=us*m*g*d
1/2*18*19.8^2 - 1225=us*18*9.8*15.36
us=0.85
frictional coefficient, us=0.85
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