JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Laws of Motion

A body of mass 10 kg is moving with an initial speed of

20 m/s

. The body stops after 5 s due to friction between body and the floor. The value of the coefficient of friction is: (Take acceleration due to gravity

g = 10 ms^{- 2}

)

(A)0.2
(B)0.3
(C)0.5
(D)0.4✓ Correct

Answer: (D)

Solution

Friction alone halts the body, slowing it from

20 m s^{- 1}

to rest in

5 s

, so its retardation is

a = \frac{20}{5} = 4 m s^{- 2}

. The only horizontal force is kinetic friction,

μ m g = ma

, and the mass cancels to leave

μ = \frac{a}{g} = \frac{4}{10}

. The coefficient of friction is

0.4

JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Single correct option

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