Question

Calculate the work done by the force of gravity to pull a $10kg$ box down a ${30}^0$ inclined plane of length $8.0m$? Note that $\sin {30}^0=\cos {60}^0=0.500$ and $\cos {30}^0=\sin {60}^0=0.866$.

• A. $40J$
• B. $69J$
• C. $400J$
• D. $690J$
• E. $800J$

Answer 1

The correct option is C $400J$

Given : $m=10kg$ $l=8.0$ m

Work done by gravitational force $W=\left(mgsin{30}^o\right)l$

$\therefore$ $W=(10\times 10\times 0.5)\times 8.0=400$ J