Question

A block of mass 2 kg is pulled upwards by a force $F=40N$ as shown in figure. Block is displaced by $2m$. Find work done by the applied force and also due to the force of gravity on the block. (Take $g=10m/s^2$)

• A. $-40J,80J$
• B. $80J,-40J$
• C. $80J,40J$
• D. $-80J,-40J$

Answer 1

The correct option is B $80J,-40J$

Work done by applied force on the block=$F\times s$

$=F\times s$

$=40\times 2$

$=80J$

Work done gravitational force on the object=$mg\times s$

$=mg(-s)$ (-ve sign as direction of displacement and force is opposite here)

$=2\times 10\times -2$

$=-40J$