Free Fall
By: Jasmine Ahmed, Shelley Bi,
Christina Bai
What is Free Fall?
• Free fall is the motion of an object falling with a
constant acceleration
• In this case, the constant acceleration would be
a = g = 9.81 m/s2, but since objects free
fall
towards the Earth's surface ---> a = - g = 9.81 m/s2
• When there is no air resistance, all objects fall with the
same acceleration regardless of their masses
For Example . . .
If an astronaut dropped a
hammer and a feather in
space, the hammer and the
feather would fall towards
the surface with the same
acceleration, therefore they
would land on the surface at
the exact same time.
In free fall, the acceleration, 9.81
m/s2, remains constant. This occurs,
because of the gravity near the
Earth's surface.
V = at
To find the distance traveled by an
object during free fall, we use the
formula, where a=g
d= vit + 1/2
2
at
When an object starts at rest, the
formula is reduced to
d= 1/2
2
at ,
because the velocity is 0 m/s.
Problem 1
A ball dropped from rest falls freely until it
hits the ground with a speed of 20 meters per
second. The time during which the ball is in
free fall is approximately
(1) 1 s
(2) 2 s
(3) 0.5 s
(4) 10 s
Solution to Problem 1
V = at
t=V
a
t = 20 m/s
-9.81 m/s^2
(2) t = 2 seconds
Problem 2
An object is allowed to fall freely near the
surface of a planet. The object has an
acceleration due to gravity of 24 m/s2 How
far will the object fall during the first
second?
(1) 24 meters
(3) 9.8 meters
(2) 12 meters
(4) 4.9 meters
Solution to Problem 2
d= 1/2 at2
d= 1/2 (24 m/s2)(1s)
(2) d= 12 m
Problem 3
3. Starting from rest, object A falls freely
for 2.0 seconds, and object B falls freely for
4.0 seconds. Compared with object A, object
B falls
(1) one-half as far
as
(2) twice as far
(3) three times
far
(4) four times as far
Solution to Problem 3
d= 1/2 at2
d= 1/2(-9.81m/s2)(2s)2
d= 19.62 m
d= 1/2 at2
s )
d= 1/2(-9.81m/s2)(4 2
d= 78.48 m (4) four times as far
http://www.youtube.com/wat
ch?v=PE81zGhnb0w
http://www.youtube.com/wat
ch?v=3BETTsLOgQI
Homework
Midyear review problems
#4 and #27
Amsco p. 25 #15 and #16