4. Important note
• Free fall does not mean that the object
is falling down only.
• Objects thrown upward or downward and
those released from rest are all the
examples of free fall.
5. Falling objects & air resistance
More air resistance on without
crumpled-up piece of paper
Less air resistance on
crumpled-up piece of paper
6. Falling objects & air resistance
In vacuum both feather and apple
falls at the same rate.
Reason:
In vacuum there is no air, it means
there is no air resistance.
So surface area and mass makes
no difference.
7. Acceleration due to gravity
0 s, v1 = 0 m/s
1 s, v2 = 9.8 m/s
2 s, v3 = 19.6 m/s
3 s, v4 = 29.4 m/s
4 s, v5 = 39.2 m/s
• During each second of fall, the speed
of a ball changes by 9.8 m/s.
• The change in speed is due to gravity.
• Hence, the acceleration in this case is
called acceleration due to gravity.
𝑔 = 9.8 m/s2
9. Equations of motion for free fall
Kinematical equations of motion is also applicable for free fall
because, free fall is an example of uniformly accelerated motion.
HORIZONTAL MOTION FREE FALL
vf = vi + at vf = vi − 𝑔t
xf − xi = vit +
1
2
at2
yf − yi = vit −
1
2
𝑔t2
vf
2
= vi
2
+ 2a(xf − xi) vf
2
= vi
2
− 2𝑔(yf − yi)
10. Position-time graph for free fall
Time (s) Position (m)
0 0
1 -4.9
2 -19.6
3 -44.1
4 -78.4
5 -122.5
1 2 3 4 5 6
t
0
-40
-20
-60
y
-100
-80
-120
11. Velocity-time graph for free fall
Time (s) Velocity (m/s)
0 0
1 -9.8
2 -19.6
3 -29.4
4 -39.2
5 -49
1 2 3 4 5 6
t
0
-20
-10
-30
v
-50
-40
-60
12. Acceleration-time graph for free fall
Time (s)
Acceleration
(m/s𝟐
)
0 -9.8
1 -9.8
2 -9.8
3 -9.8
4 -9.8
5 -9.8
1 2 3 4 5 6
t
0
-4
-2
a
-6
-8
-10
-12
