Question

Two high school students attempt to push a car uphill. The car rolls downhill against them for a distance of $10m$ before they can bring it to a stop. If both students pushed on the car with a force of $1000N$ while it rolled downhill, how much work did they do?

• A. $0$
• B. $1000J$
• C. $-1000J$
• D. $10,000J$
• E. $-10,000J$

Answer 1

The correct option is A $0$

Work done by a force $\overrightarrow{F}$ is given by ,

$W=\overrightarrow{F}.\overrightarrow{d}$ , where $\overrightarrow{d}=$ is the displacement ,

in the given example , displacement $\overrightarrow{d}$ , due to the force of $1000N$ is zero , therefore work done by students is also zero .

One can say that there is a displacement of 10m , but that is due to gravitational force , not due to the force applied by students .