Example 3.1.4.
Find the power a horse who does 7460 J of work in 10 second.
Solution.
\begin{align*}
P \amp =\frac{W}{t} \\
or, P \amp =\frac{7460}{10} \\
\therefore P \amp =746 watt
\end{align*}
746 watt of power is also called 1 horsepower.
Subsection 3.1.2 power
The rate of doing work is called power . It is also the rate at which the energy can be transfered. Power tell us that how fast the work has been done. Power can be expressed as
\begin{equation}
P =\frac{W}{t}\tag{3.1.6}
\end{equation}
\begin{align*}
or, P \amp = \frac{Fd}{t} \\
or, P \amp = F\frac{d}{t} \\
\therefore P \amp = F v
\end{align*}
Its SI unit is Watt (w=j/s).
Example 3.1.5.
A car engine of 200kW power pushes the car to 25 m/s. Find the thrust (force) produces by its engine.
Solution.
\begin{align*}
P \amp =F v\\
or, F \amp =\frac{P}{v} \\
\therefore F \amp = \frac{200\times 1000}{25} = 8000 N.
\end{align*}
