Page 76 - eEISBN FINALIZE

1
then; = ( + )
2
2
2

1
= (20 + 0)8.25
2
2

= .
2

then; = +
1
2

= 60.94 − 82.5

= .

5.2.3 Motion Under gravitational Force

Use the formulae for constant acceleration to model an object moving

vertically in a straight line under gravity.

• The force of gravity causes all objects to accelerate towards the earth. If you ignore the

effects of air resistance, this acceleration is constant. It does not depend on the mass of the
object.This means that in a vacuum an apple and a feather would both accelerate

downwards at the same rate.

• On earth, the acceleration due to gravity is represented by the letter g and is approximately
-2
9.8 ms . The actual value of the acceleration can vary by very small amounts in different
places due to the changing radius of the Earth and height above sea level.
-2
Always use g = 9.8 ms . This is an approximation to two significant figures. If you use this value
in your working you should give you answer to the same degree of accuracy.

67