MOTION, WORK AND POWER.

Speed is the distance moved per unit time.

Speed = distance/time.

The speed triangle.
	Many speed problems can be solved using the speed triangle. (Think of Eat my dust!) The following examples will show how to use it.

Examples.

Question A boy walks a distance of 10 km in 5 hours. Calculate his average speed.
	Here, we are looking for the speed. So we cover the letter S. This gives us D over T. Answer. Speed = distance/time = 10/5 = 2 km/hr.

Question A car travels at a speed of 60 km/hr. Calculate the distance it travels in 3 hours..
	Here, we are looking for the distance. So we cover the letter D. This gives us S by T. Answer. distance = speed x time = 60x3 = 180 km..

Question A horse is running at a speed of 12 km/hr. How long will it take to travel 18 km?
	Here, we are looking for the time. So we cover the letter T. This gives us D over S. Answer. time = distance/speed = 18/12 = 1.5 hr.

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Velocity is distance travelled per unit time in a particular direction.

Acceleration is the change in speed per unit time.

The unit of acceleration is the m/s per second or m/s².

Question
A car is travelling at a speed of 10 m/s. It increases its speed to 34 m/s in a time of 8 seconds. Find its acceleration.

Answer.

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Work is done when a force moves something.

Work done = Force x distance moved.

The S.I. unit of work is the joule.

One joule of work is done when a force of 1 N moves a body a distance of 1 m.

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The power of a machine is the amount of work it does per second.

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