Answer to Question #229301 in Mechanics | Relativity for Anand

Question #229301
A child of mass 30 kg slides from rest down a wooden pole by a distance of 3.0 m. Calculate the average force of friction acting on the child if her speed is 2 m/s.
when she hits the ground.
Take g = 10m/s
1
Expert's answer
2021-08-25T18:13:20-0400

start by calculating the acceleration using the third equation of motion

v2=u2+2asv^2=u^2+2as

from rest u=0

22=02+2(a)(3)2^2=0^2+2(a)(3)

4=6a,a=0.67m/s24=6a, a=0.67m/s^2

now a=Fnetm=mgfrictionforcema=\frac{F_{net}}{m}=\frac{mg-friction force}{m}

ma=mgfrictionforcema=mg-friction force

frictionforce=mamg=30×0.6730×10=279.9Nfriction force=ma-mg=30\times 0.67-30\times 10=-279.9N

so the average friction force which is acting in the opposite direction is 279.9N


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