Question

A toy car of mass 6 kg initially moves with a speed of 3 m/s. How much work must be done on the car to increase its speed to 7 m/s?

Answer 1

120 J

Explanation:

We must calculate the kinetic energy in both cases, with the speed at 3 m/s and the speed at 7 m/s, the energy difference is the necessary work.

`\begin{gathered} KE=(1)/(2)m\cdot v^2 \\ \text{ Thefore::} \\ KE=(1)/(2)\cdot6\cdot3^2=(1)/(2)\cdot6\cdot9=27 \\ KE=(1)/(2)\cdot6\cdot7^2=(1)/(2)\cdot6\cdot49=147 \end{gathered}`

Now, we calculate the work like this:

`\begin{gathered} W=\Delta KE=147-27 \\ W=120\text{ J} \end{gathered}`

Work is 120 J