Transcript
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
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