Question

Sneha has to lift a load of mass 50 kg to a height 1m. She can exert a maximum effort of 250 N, so she uses an inclined plane to lift the load up. What should be the minimum length of the plank used by her?

• A. 2m
• B. 1m
• C. 2.5m
• D. 1.5m

Answer 1

The correct option is A

2m

Effort required in lifting 50 kg to a height of 1m is,

E = mgh = 50 $\times$ 10 $\times$ 1 = 500 N

E = 250 N, h = 1m, L = 50 $\times$ 10 = 500 N

But, E = L sin $\theta$

250 = 500 sin $\theta$

sin $\theta$ = $\frac{250}{500}$ = $\frac{1}{2}$

sin $\theta$ = $\frac{h}{l}$ = $\frac{1}{2}$

$\frac{1}{l}$ = $\frac{1}{2}$

l = 2m