A man uses a crowbar 2 m long to lift a concrete block weighing 600 N as shown in Figure 1.96. Calculate the position of the pivot if an effort of 150 N is applied. Determine: a) the mechanical advantage, b) velocity ratio, c) efficiency of the lever.

Kila ngazi ina urefu wa $20 \text{ cm}$, ambayo ni sawa na $0.20 \text{ m}$. Kuna ngazi 50.

$$\text{Urefu jumla} (h) = \text{Idadi ya ngazi} \times \text{Urefu wa kila ngazi}$$ $$h = 50 \times 0.20 \text{ m}$$ $$h = 10 \text{ m}$$

Kazi iliyofanywa ($W$) ni sawa na nishati uwezo iliyopatikana, ambayo hutolewa na formula $W = mgh$, ambapo $m$ ni uzito, $g$ ni mvutano wa mvuto ($9.8 \text{ m/s}^2$), na $h$ ni urefu jumla.

$$W = mgh$$ $$W = 40 \text{ kg} \times 9.8 \text{ m/s}^2 \times 10 \text{ m}$$ $$W = 3920 \text{ J}$$

Nguvu ya wastani ($P$) hutolewa na formula $P = \frac{W}{t}$, ambapo $W$ ni kazi iliyofanywa na $t$ ni muda uliotumika.

$$P = \frac{3920 \text{ J}}{5 \text{ s}}$$ $$P = 784 \text{ W}$$

Nguvu ya wastani ya mtu huyo ni $\boxed{\text{784 W}}$.