An automobile steering wheel is shown. What is the ideal mechanical advantage? If the AMA is 8, what is the efficiency of the steering wheel?

1. Ideal Mechanical Advantage (IMA): 9
Explanation:
For a wheel and axle system like the steering wheel, the IMA is given by:
[tex]IMA=\frac{r_w}{r_a}[/tex]
where
[tex]r_w[/tex] is the radius of the wheel
[tex]r_a[/tex] is the radius of the axle
For the steering wheel of the problem, we see that [tex]r_w = 18 cm[/tex] and [tex]r_a=2 cm[/tex], so the IMA is
[tex]IMA=\frac{18 cm}{2 cm}=9[/tex]
2. Efficiency: 88.9%
Explanation:
The efficiency of a system is defined as the ratio between the AMA (actual mechanical advantage) and the IMA:
[tex]\eta=\frac{AMA}{IMA}\cdot 100[/tex]
In this problem, AMA=8 and IMA=9, so the efficiency is
[tex]\eta=\frac{8}{9}\cdot 100=88.9\%[/tex]