A block of mass 10 kg is moving up an inclined plane of inclination 30° with an initial speed of 5 m/s. It stops after 0.5 s, what is the value of coefficient of kinetic friction?
Text Solution
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For equilibrium, normal to pane
N = mg cos θ …
Net force along the plane downward
F = mg sin θ + fk …
where fk is kinetic friction
but fk = μ N = μ mg cos θ …
from eq. , , and we get
∴ F = mg sin θ + μ mg cos θ

According to Newton’s IInd law
F = ma
∴ ma = mg sin θ + μ mg cos θ
∴ Retardation a = g sin θ + μ g cos θ
From equation v = u + at, (we have)
o = u – (g sin θ + μ g cos θ ) t
⇒ g sin θ + m g cos θ = 
⇒ 10 × sin 30° + × 10 cos 30° = 
⇒ 10 ×
+ 10 μ ×
= 10
⇒ 5
μ = 5
or μ = 
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