Physics

Power


Two cars leave the beach towards the mountains (h = 600m). One car travels in 1 hour, the other takes 2 hours to arrive. Which car did the most work?

Neither. The work was exactly the same. However, the fastest car has developed a higher horsepower.

The power unit in SI is watt (W).

In addition to the watt, the units are often used:

1kW (1 kilowatt) = 1000W

1MW (1 megawatt) = 1000000W = 1000kW

1hp (1 horsepower) = 735W

1HP (1 horsepower) = 746W

Average power

From this we define average power relating the Work with the time taken to perform it:

How do we know that:

So:

Instant Power

When the time spent is infinitely small we will have instantaneous power, ie:

Example:

What is the average power that a body develops when applied to it a horizontal force with intensity of 12N, for a course of 30m, and the time taken to travel it was 10s?

What about instant power when the body reaches 2m / s?