Transcript Projectile Motion Notes

Projectile Motion
Consider bodies acted upon by some force…
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What do they all have?
ACCELERATION
Consider direction of applied force or
acceleration…
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In direction of motion  +a
Opposite direction of motion  -a
At right angles to direction of motion  circular
At right angles to initial direction of motion 
parabolic
vi
F
Parabolic Conditions
Force at right angles to initial velocity
Constant velocity in one direction
Ex. Gravity w/ bomb, arrow, bullet
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Full parabolas  golf ball, football
Consider motion in horizontal & vertical directions
Horizontal
Vertical
• No additional horizontal forces
• -g on way up
• Object in motion stays in motion
• -g on way down
• vx is constant
• F = ma
• 1 equation vx = dx/t
• vf=√2ad+vi2
• D= ½ at2 + vit
• vf=vi + at
• vy decreases on way up
• vy increases on way down (in
negative direction)
Which will hit the ground 1st?
Bullet dropped or fired?
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Ball hit off the table with a ruler
Ball hit/dropped at the same time
Plane and bomb to observer on ground
To in plane observer – straight down
Example
Gum wad and Car:
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Straight Down?
Backwards parabola?
Forward parabola?
Object in motion stays in motion
Air friction – slows down
Gravity – travels down
More Examples…
Golf: Hit hard for far and not for close?
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NOT ALWAYS
Angles determine distance
Different clubs and swings
Arrows
Javelin: too large  too much air friction
Basketball: only part of parabola
Objects fired will drop…
An object fired forward will drop. How
much?
Gun 357 Magnum
Muzzle v = 1295 ft/s
Distance Velocity
50 yards 1094 ft/s
100 yards 975 ft/s
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Drop
0.8 inches
3.5 inches
To compensate
Baseball
Throw from above
 Elevate mound
Fastball Velocity Mound to Plate Time Drop
85 mi/hr
55 ft
.46s 3.3 ft
90 mi/hr
55 ft
.44s 3 ft
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Rising Fastball?
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Not really – rotates at 10,000 rpm
Backspin enough for a 6” rise, therefore it only
drops 2.8 or 2.5 feet
If throwing from 3rd to 1st – 120 ft at 85 mi/hr
If launch at 8° can’t deviate by more than 2° aim 16 ft over 1st baseman
To keep a projectile in the air longer
adjust:
To keep a projectile in the air longer
adjust:
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Velocity (higher)
Angle (larger)
Largest angle is 90° straight up – in air
long but no horizontal distance
Greatest height – largest angle and largest
velocity
Maximum range (dx) = 45°
http://youtube.com/watch?v=Wsq3dWTrR
WA