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Tuesday, December 18, 2012

Eleven Plus Acceleration

It looks as if some of our eleven plus children may have to do some different types of mathematics in the years ahead. Do you remember doing these little equations at school?

V2= u2  + 2as

Can you recall your science teacher, garbed in a white coat, holding a piece of chalk explaining acceleration to the class? Did your teacher take you, and your class, up to the roof of the school to demonstrate the speed of a body falling? (No – not a classmate falling but an inanimate object!)

You are given the following information:
The body (u) falls at 30 metres per second
It accelerates (a) at 2 metres per second
It takes (t) 10 seconds
To reach a velocity (v)

To find velocity:
V = at + u = (2 x 10) + 30 = 50 metres per second
To find speed:
S = ut + ½ at2 = (30 x 10) = (1/2 x 2 x 102)

Your eleven plus child will tell you in a few seconds that:
300 + 100 = 400 metres

So the average speed is the distance travelled (s) divided by t.
100 divided by 10 = 40 metres per second.

Now for the eleven plus question:

If the body starts travelling at 30 metres per second what speed will the body reach?

A 50
B 70
C 20
D 80