A wheel and axle have radii 80cm and 10 cm respectively. If the efficiency of the machine is 0.85, what load will an applied force of 1200N to the wheel raise?

The velocity ratio for a wheel and axle is the ratio of the wheel's radius to the axle's radius.

$$VR = \frac{R_W}{R_A}$$ $$VR = \frac{0.8 \text{ m}}{0.1 \text{ m}} = 8$$

The efficiency of a machine is given by the ratio of its mechanical advantage to its velocity ratio.

$$\eta = \frac{MA}{VR}$$

Rearrange to solve for MA:

$$MA = \eta \times VR$$ $$MA = 0.85 \times 8$$ $$MA = 6.8$$

The mechanical advantage is also defined as the ratio of the load to the effort.

$$MA = \frac{F_L}{F_E}$$

Rearrange to solve for $F_L$:

$$F_L = MA \times F_E$$ $$F_L = 6.8 \times 1200 \text{ N}$$ $$F_L = 8160 \text{ N}$$

The load that an applied force of $1200 \text{ N}$ will raise is $\boxed{8160 \text{ N}}$.