2. Objectives
state equations which represent uniformly
accelerated motion in a straight line
state that the acceleration of free fall for a body
near to the Earth is constant and is approximately
10 m/s2
solve problems using equations which represent
uniformly accelerated motion in a straight line,
including the motion of bodies falling in a uniform
gravitational field without air resistance
3. Equations of Motion
From graph,
a = (20-0) / (5-0)
= 4 ms-2
Therefore, a = (v-u) / t ...(1)
Where v is final velocity
u is initial velocity
Average velocity
<v> = s / t = (v-u)/2…(2)(Equation 1)
4. Equations of Motion
From (1), you will get
v = u + at ---(3) (Equation 2)
Multiply (2) to (1),
sa/t = (v+u)(v-u)/2t
sa/t = (v2-u2)/2t
2as = v2-u2
v2 = u2 + 2as ---(4) (Equation 3)
5. Equations of Motion
Substitute (3) into (2)
s/t = (u+at+u)/2
s/t = u + (1/2)at
s = ut + ½(at2)…(5) (Equation 4)
6. Summary of Equations
<v> = (v + u)/2 = s/t
a = (v - u)/t
v = u + at
v2 = u2 + 2as
s = ut + ½at2
7. Free-Fall
A free-falling object is one which is falling under the
influence of gravity
Only force acting on it is WEIGHT
2 characteristics of free fall
Objects do not encounter air resistance
Accelerating downwards towards ground at a rate of
approx. 10 ms-2
