Students will learn about free fall: when the only acceleration acting on a body is the acceleration due to gravity.

1. PHYSICS
FREE FALL

2. LET’S START

3. DEFINITION
Free fall is the motion of an object under the effect of
gravitational force only

4. 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

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
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.

8. EXAMPLES:
Dropped
Thrown downward
Thrown upward

9. SIGN CONVENTION

10. 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

11. POSITION-TIME GRAPH FOR FREE FALL

12. DROPPED

13. DROPPED FROM XO = 0
Time (s)
o
Position
(m)
Parabola

14. VELOCITY-TIME GRAPH FOR FREE FALL

15. ACCELERATION-TIME GRAPH FOR FREE FALL

16. THROWN UPWARDS FROM XO = 0

17. HAMMERS AND FEATHERS
At a given location on the
earth and in the absence
of air resistance, all
objects fall with the same
uniform acceleration.
Thus, two objects of
different sizes and
weights, such as hammers
and feathers, dropped
from the same height will
hit the ground at the same
time.

18. AVERAGE VELOCITY
at
v
v i
f 

t = 0 vi = 0 m/s
t = 1 s v = -9.81 m/s
t = 2 s v = -19.62 m/s
t = 3 s v = -29.43 m/s
An object falls from rest. Calculate its velocity
at the end of one second. Two seconds. Three
seconds.

19. FREE FALL
Top 5 Facts for objects thrown straight up & free fall!
“g” is ALWAYS -9.8 m/s2
If thrown up, the velocity is zero at max height!
Time going up = Time going down
All kinematic equations may be used for vertical projectiles… EXCEPT
V = d/t and
V = (Vf + Vii)/2
Even at max height when final velocity is zero, “g” is still -9.8 m/s2

20. 1 - QUIZ
What is the velocity and
acceleration at the top of the
motion?

21. 2 - QUIZ
A rock is dropped from an 80-meter cliff. How long
does it take to reach the ground?

22. 3 - QUIZ
One second after being thrown straight down, an
object is falling with a speed of 20 m/s. How fast
will it be falling 2 seconds later?

23. 4 - QUIZ
Tayyar throws a ball upward with initial speed of 20 m/s.
How high will it go? How long will it take for the ball to come
back?

24. LESSON TAKEAWAYS!

25. THANK YOU!