JEE Main · 2004 · 24 Apr 2004 · Offline · Laws of Motion

A block rests on a rough inclined plane making an angle of

3 0^{\circ}

with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is (take

g = 10 m / s^{2}

)

(A)2.0✓ Correct
(B)4.0
(C)1.6
(D)2.5

Answer: (A)

Solution

The block rests on the incline, so friction alone balances the component of weight down the surface,

f = m g sin 3 0^{\circ}

. With

f = 10

N and

sin 3 0^{\circ} = \frac{1}{2}

, we have

10 = m \times 10 \times \frac{1}{2}

, which gives a mass of

2

kg.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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