Question

A block of wood mass $5kg$ is placed on a plane making an angle ${30}^o$ with the horizontal. If the coefficient of friction between the surface of contact of the body and the plane is $0.5$. What force is required to keep the body sliding down with uniform velocity?

• A. $1.6N$
• B. $4.8N$
• C. $6.4N$
• D. $3.35N$

Answer 1

The correct option is D $3.35N$

From FBD of block

$N=mgcos\theta$

and

$mgsin\theta =F+f$

$F=mgsin\theta -f$

$F=50\times 1/2-0.5\times 50\times 0.866$

$F=25-21.65$

$F=3.35N$

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