Speed

Content

Section 4 --- Speed

In this page:

	What is speed?
	Worked Example
	Quiz
	Answers for the Quiz

What is speed?

Speed is actually a example of rate but it is only used for the measurement of how fast an object travels.

E.g. A car travels at 50 km/h.

      A bicycle travels at 8 m/s.

      John walked at a speed of 14 m/min.

      Light travels at 300 000 km/s.

These are all examples of speed.

Worked Example

Mr. Kong started to travel from Town A to Town C at 9 a.m. He reached Town B at 12.30 p.m. after travelling at an average speed of 90 km/h and had a 1 hour break. Then, he proceeded to Town C at an average speed of 110 km/h and reached there at 3 p.m. What is the average speed for the whole journey?

Total Time                                                                          = (1230 - 0900) + (1500 - 1330) + 1 h                                  = 3 h 30 min + 1 h 30 min + 1 h                                              = 6 h

Total Distance                                                                    = (90 x ) + (110 x )                                                        = 315 + 165                                                                         = 480 km

Average Speed For Whole Journey                                      = km/h                                                                        = 80 km/h

Quiz

1. Miss Tan started to travel from Town X to Town Z at 6 a.m. She reached Town Y at 2.30 p.m. after travelling at an average speed of 70 km/h and had a 2 hours' break. Then, she proceeded to Town Z at an average speed of 120 km/h and reached there at 7 p.m. What is the average speed for the whole journey?

2. A car started its journey from Town S to Town T at 0800. At the same time, the bus started its journey from Town T to Town S. The car travelled at 85 km/h while the bus travelled at 50 km/h. At a certain time, the bus and car met each other at Point X. Given that the distance between Town S and Town T is 810 km, find out the following:

(a) What time did the bus and car meet? (b) What is the distance covered by the bus when it met the car? (c) (i)At what speed must the car travel so that it can reach Town T at 1630? (ii) Thus, what is the average speed of the car for the whole journey?

Ready? Click here for the answers.