QJEEM21Ph53a4: JEE Main 2021 Physics - Class 11 JEEM21Ph53a4 Solution: A body of mass 'm' is launched up on a rough inclined plane…

Question

Verified Solution • 2025–26 Session moderate

A body of mass 'm' is launched up on a rough inclined plane making an angle of 30

^{\circ}

with the horizontal. The coefficient of friction between the body and plane is

\frac{\sqrt{x}}{5}

if the time of ascent is half of the time of descent. The value of x is __________.

Accepted Answer

t_{a} = \frac{1}{2} t_{d}

\sqrt{\frac{2 s}{a_{a}}} = \frac{1}{2} \sqrt{\frac{2 s}{a_{d}}}

..... (i)

a_{a} = g \sin θ + μ g \cos θ

= \frac{g}{2} + \frac{\sqrt{3}}{2} μ g

a_{d} = g \sin θ - μ g \cos θ

= \frac{g}{2} - \frac{\sqrt{3}}{2} μ g

using the above values of a_a and a_d and putting in equation (i) we will gate

μ = \frac{\sqrt{3}}{5}

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