Question

With the help of a car jack, a person lifts a $1.2$ tonne car. If the jack’s MA is $8$, how many times has the person’s effort been reduced by in lifting the car compared to when there is no jack? (Take $g$= $10{\text{m s}}^{–2}$)

• A. $8$
• B. $80$
• C. $12.5$
• D. $1.25$

Answer 1

The correct option is A $8$

The mechanical advantage $\left(\text{MA}\right)$ is the measure of how the machine eases the task for which it is operated.

Without the car jack, the person would need to put an effort equal to the load (weight of the car) in magnitude to lift the car.
$⟹\text{MA}=\frac{\text{Load}}{\text{Effort}}$
$\text{Effort}=\frac{\text{Load}}{8}$

Therefore, using the car jack, the person effort would be reduced by $8$ times compared to when there was no jack.