Question

In travelling a distance of 0.5m, an object gained 200 Joules of kinetic energy.

What work was done on the object, assuming no frictional forces acted?

What was the average forces acting on the object?

If a force of 600N had acted over the same distance, what would have been the gain in kinetic energy?

Answer 1

According to work-energy theorem,"work done on a body is equal to the change in its kinetic energy".

Let a work "W" is done on a body due to which its kinetic energy changes to $\Delta K$ then-

       $W=\Delta K$

here $\Delta K=200 J$

so work done on the object-

$\mathbf{W=\Delta K=200J}$

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Since-

Work done =Force x Displacement

$\Rightarrow 200=F\times 0.5$

$\Rightarrow F=\frac{200}{0.5}N$

$\mathbf{\Rightarrow F=400N}$

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Gain in kinetic energy=Work done on the object=force x displacement

$\Rightarrow \Delta K=F\times d$

$\Rightarrow \Delta K=600\times 0.5$$\mathbf{\Rightarrow \Delta K=300J}$