Q

# Give answer! - Laws of motion - JEE Main-2

A body of mass 2 kg slides down with anacceleration of 3 $m/{s^{2}}$ on a rough inclined plane having a slope of $30^0$. The external force required to take the same body up the plane with the same acceleration will be : (g=10 $m/{s^{2}}$)

• Option 1)

14N

• Option 2)

20N

• Option 3)

6N

• Option 4)

4N

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N

As we have learnt

Retardation of block sliding up over a rough Inclined plane -

$ma=mg\ sin\theta+F$

$ma=mg\ sin\theta+\mu mg\ cos\theta$

$ma=g[sin\theta+\mu cos\theta]$

- wherein

For $\mu=0$

$a =g\left ( sin\Theta -\mu cos\Theta \right )\rightarrow (1)$

To move body up with same accelaration

$F-\left ( \mu\: mg\: cos\Theta +mg\: sin\Theta \right ) =m\left ( g\: sin\Theta -\mu\: g\: cos\Theta \right )$

$F=2.m\: g\: sin\Theta$

$F=20N$

Option 1)

14N

Option 2)

20N

Option 3)

6N

Option 4)

4N

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