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Which velocity, V_{x} or V_{y }, is constant
for a projectile?

Projectile Motion  Volleyball
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Projectile Motion
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Projectile
Where V_{ix} = 25 m/s
V_{iy} = 40 m/s
t
(sec) 
V_{x}
(m/s) 
V_{y}
(m/s) 
0 
25 
40 
1 
25 
30 
2 
25 
20 
3 
25 
10 
4 
25 
0
(peak) 
5 
25 
10 
6 
25 
20 
7 
25 
30 
8 
25 
40 
4. Word Problems
www.sihunt.co.uk Russian long jumper Tayana
Lebedeva performs a
double hitch action in the 2007 world finals in
Osaka Japan.
Ex) An athlete doing a running jump leaves ground at an
angle of 25.° and a velocity of 10. m/s.
(a) What is the initial
vertical component (V_{iy}) of the athlete's velocity?

Ex) An athlete doing a
running jump leaves ground at an angle of 25.°
and a velocity of
10. m/s.
(a) What is
the
initial vertical component (V_{iy})
of the athlete's velocity?
V_{iy} = V_{i}sinӨ
= (10. m/s)sin25.°
= 4.2 m/s up
(b) How long
does it take for
the athlete to reach her maximum height?
(b)
How long does it
take for
the athlete to reach her
maximum height?
X 
Y 
t = ? 
V_{iy }
= 4.2 m/s
(from before) 

t = ?


V_{fy}=
0
(peak) 

a_{y}
= 9.8 m/s^{2
} 
V_{f}
= V_{i}
+ at
0 =4.2 m/s+(9.8 m/s^{2})t
(subtract 4.2 m/s from both sides)
 4.2 m/s = (9.8 m/s^{2})t
( 4.2 m/s)/(9.8 m/s^{2}) = t
t = .43 secs
to reach peak
(c) How long
did it take for the athlete to complete the entire jump?
(c) How
long
did it take the athlete to complete her entire
jump?
On level ground
Total time =
double
peak time 
Entire
Jump:
Total Time = .86 seconds
(c) How
far did she jump?
(c) How far
did she jump?
d_{x} = ?
t = .86 sec
d_{x} = V_{x}t
(Must find V_{x }
first)
V_{x}
= VcosӨ
V_{x} = (10. m/s)cos25.°
V_{x} = 9.1 m/s
d_{x} = 9.1 m/s(.86 sec)
d_{x} = 7.8 m
Projectile
Problems II
ŠTony Mangiacapre.,
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