Question

a machine makes work easier by doing all of the following, except
changing the force.
changing the direction.
changing the distance.
changing the acceleration.
question #9
if the radius of a doorknob is 4.5 cm and the radius of its inner rod is 0.5 cm, what is the mechanical advantage of the doorknob?
9.0
0.11
0.5
2.25

Explanation:

First question

Machines make work easier by changing force, direction, or distance. They do not directly change acceleration to make work easier.

Step1: Recall mechanical - advantage formula for wheel - and - axle

The mechanical advantage (MA) of a wheel - and - axle (a doorknob is an example of a wheel - and - axle) is given by the ratio of the radius of the wheel ($R$) to the radius of the axle ($r$), i.e., $MA=\frac{R}{r}$.

Step2: Identify values of $R$ and $r$

Here, $R = 4.5$ cm (radius of the doorknob) and $r=0.5$ cm (radius of the inner rod).

Step3: Calculate mechanical advantage

$MA=\frac{4.5}{0.5}=9$

Answer:

Changing the acceleration

Second question