FREE FALL

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

Free fall

Motion of bungee jumper Motion of skydivers

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.

Falling objects & air resistance

More air resistance on withoutcrumpled-up piece of paper

Less air resistance oncrumpled-up piece of paper

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.

Acceleration due to gravity0 s,

1 s,

2 s,

3 s,

4 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=9.8m /s2

Sign conventionPosition Velocity Acceleration

y > 0

y < 0

0 0

y y y y

v > 0 v < 0a = -g

y

Equations of motion for free fallKinematical equations of motion is also applicable for free fall because, free fall is an example of uniformly accelerated motion.

HORIZONTAL MOTION FREE FALL

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 t0

-40

-20

-60

y

-100

-80

-120

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 t0

-20

-10

-30

v

-50

-40

-60

Acceleration-time graph for free fall

Time (s) Acceleration (m/)

0 -9.8

1 -9.8

2 -9.8

3 -9.8

4 -9.8

5 -9.8

1 2 3 4 5 6 t0

-4

-2

a

-6

-8

-10

-12

Thankyou