Question

A horizontal force F is exerted on a 20 kg block to
push it up an inclined plane having an inclination of
30°. The frictional force retarding the motion is 80 N.
For the acceleration of the moving block to be zero, the
force F must be:
30°​

Answer 1

Answer:

F = 20 N

Explanation:

net acceleration is zero

that implies net force is zero

that implies F = mgsin(theta) - frictional force

Answer 2

The acceleration of the moving block to be zero, the force F must be 207.84 N.

Explanation:

Given that,

Mass of the block, m = 20 kg

Angle of inclination of the block, $\theta=30^{\circ}$

The frictional force retarding the motion is 80 N, f = 80 N

For the acceleration of the moving block to be zero, the net force acting on it can be given by :

$F\cos\theta=mg\sin\theta+f\\\\F\cos(30)=20\times 10\times \sin(30)+80\\\\F\cos(30)=180\\\\F=\dfrac{180}{\cos(30)}\\\\F=207.84\ N$

So, the acceleration of the moving block to be zero, the force F must be 207.84 N.

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