Question

How much work does the force of gravity do in pulling a 10 kg box down a ${30}^o$ inclined plane of length 8.0 m? Note that $sin{30}^0=cos{60}^0=0.500$ and $cos{30}^0=sin{60}^0$= 0.866.

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

Answer 1

The correct option is C 400 J

Given - $d=8.0m$ , $m=10kg$ , $\theta ={30}^o$ ,

now , acceleration due to gravity would be the component of $g$ parallel to the inclined plane i.e. $a=g\sin \theta$ ,

therefore force due to gravity $F=ma=mg\sin \theta$ ,

$F=10\times 10\times \sin 30=100\times 1/2=50N$ ,

now work done due to gravity $W=f\times d=50\times 8=400J$