Question

a block of mass m =2kg pulled by a force F =40N upwards through a height h=2m. The work done on the block by the applied force F and its weight mg are (g=10m/s2

Answer 1

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Answer 2

Answer:

Workdone on the block by the applied force = 80N.

Workdone on the block by its weight mg = -40N.

Explanation:

• Work done by the applied force F

   $W= f.d cos\alpha$         where f is applied force and d is the displacement of                      block and $\alpha$ is the angle between force and displacement.

$W = 40*2*cos 0$     (Here $\alpha$ is zero as both the force and displacement    act  along same direction.)

   $W$  $= 80 Joule$

• Work done by its weight mg

       $W= f.dcos\alpha$

        $W$  $= f.d.cos180$    (Here $\alpha$ is 180 as both force and displacement act along opposite directions)

$W = -mgd$               where $g$ is the acceleration due to gravity.( g = 10$\frac{m}{s^{2} }$)

$W = - 2 * 10* 2$        

$W = -40Joule$

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