Chapter-3
Falling Objects and Projectile
Motion
Overview:
Explore how objects move
under the influence of gravity
close to the surface of the earth.
Outline:
Acceleration due to gravity
Falling object
Projectile motion
Falling Objects
Why objects fall to the ground when released?
When you drop objects of different sizes and weights, do they
reach the ground at the same time? (Click the link below)
http://www.teachersdomain.org/resource/phy03.sci.phys.mfw.galmoon/
Measuring the acceleration due to gravity for Earth: 9.8 m/s2
Falling Object: Velocity and Distance
t (s)
Spread Sheet (Excel)
Calculations
v=v0 + at
d=v0t+1/2 at2
y = 9.8x
250
V (m/s)
200
150
100
50
0
0
5
10
15
20
25
Time (s)
2500
d (m)
2000
1500
1000
500
0
0
5
10
15
20
25
v (m/s)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0
9.8
19.6
29.4
39.2
49
58.8
68.6
78.4
88.2
98
107.8
117.6
127.4
137.2
147
156.8
166.6
176.4
186.2
196
t (s)
Reaction Time Experiment
d (m)
0
4.9
19.6
44.1
78.4
122.5
176.4
240.1
313.6
396.9
490
592.9
705.6
828.1
960.4
1102.5
1254.4
1416.1
1587.6
1768.9
1960
Throwing up a ball:
Velocity and Distance
Q: A ball is thrown straight upward and
then returns to the Earth. Does the
acceleration change during this motion?
Throwing up a ball:
Velocity VS. Time graph
Projectile Motion:
A Cartoon Coyote Falling off a Cliff
We need to consider the horizontal and vertical motions separately in
projectile motions. Time is the same for both motions.
Horizontal and Vertical motions
Q: What determines the time of flight?
A: Vertical motion
Practice Sample Exercise in example box 3.4
Angle for maximum Range
http://phet.colorado.edu/simulations/sims.php?sim=Projectile_Motion
Go to the above website and determine the angle for maximum range by firing at
different angles. ______________