71. NCERT Exemplar XXI

Exercise condition:

5 m.

Define watt.

Express kilowatt in terms of joule per second.

A \(150\ kg\) car engine develops \(500\ W\) for each kg. What force does it exert in moving the car at a speed of \(20\ m s^{-1}\)?

One watt is the of an object which does work at the rate of .

\(1\ kilowatt\ =\ 1000\ watt\)
\(1\ kilowatt\ =\ 100\ watt\)
\(1\ kilowatt\ =\ 10\ watt\)
\(1\ kilowatt\ =\ 1\ watt\)

\(1\ kilowatt\ =\ 10\ \frac{joule}{second}\)
\(1\ kilowatt\ =\ 1\ \frac{joule}{second}\)
\(1\ kilowatt\ =\ 100\ \frac{joule}{second}\)
\(1\ kilowatt\ =\ 1000\ \frac{joule}{second}\)

The formula to calculate the Power (\(P\)) is,

\(Power\ (P)\ =\ \frac{Force\ (F)}{Velocity\ (v)}\)
\(Power\ (P)\ =\ Force\ (F) \times Velocity\ (v)\)

Force exerted in moving the car \(=\) \(N\)

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