Saturday, May 5, 2012

How to get the Speed?

In Physics, it deals more on the objects at rest or in motion. But when we want to know the way objects move by getting its speed, the formula is:

speed = distance traveled/time  (/ sign is division operation)

Speed is the distance traveled divided by time taken. Remember that speed is a scalar which has no direction. The car's speedometer measures how fast the car is moving but it does not give its direction. Whether the car is going in a circle or along a straight line, it makes no difference.

Let us take this sample problem:

Lisa too her to travel at 3.0 h of a distance of 120 km/h to reach her grandmother's house. What is the average speed?

speed = 120 km/3.0 h = 40 km/h

The result doesn't necessarily mean that Lisa's car was  moving at this speed. It simply indicates that she sometimes went faster and sometimes slower than this.

Problems for you to solve as a sort of an Exercise

1. A 400-m dash at a certain school is run by making two laps around a 200-m oval track. A runner takes 70 s to run 400 m. What is her average speed?

2. From London to Athens is 2,500 airline km. What speed must an airplane have to make the trip in 3.0 h?

3. The distance from earth to moon is 385,000 km. A typical flight to the moon takes about 64 h. What is the average speed of the spaceship?

4. In 1970, the Indianapolis 500 ways won by Al Lender. He traveled the 500 miles in 3 h 13 min. What was his average speed?

5. The orbital distance around the earth for spaceship is about 43,000 kn. The time taken for the orbiting ship to make one past around the earth is about 92 minutes. What is the average speed of the ship during one pass? 

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