PASCO ME-6800 Projectile Launcher (Short Range) - Manual (Page 39)

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M o d e l N o . M E - 6 8 0 0 E x p . 9 ( D e m o ) : S i m u l t a n e o u s S h o t s a t D i f f e r e n t S p e e d s
0 1 2 - 0 5 0 4 3 G 35
Exp. 9 (Demo): Simultaneous Shots at Different Speeds
Equipment Needed
Purpose
The purpose of this demonstration is to confirm that regardless of the initial speed of projectiles fired horizontally,
the projectiles will hit the floor at the same time.
Theory
Two projectiles are shot horizontally from the same height, y. The muzzle speeds of the two projectiles are differ-
ent.
The vertical and horizontal motions of a projectile are independent of each other. The horizontal distance, x, trav-
elled by the projectile depends on the initial speed, v
0
, and the time of flight, t. The distance x = v
0
t.
The time of flight depends on the vertical distance that the projectile falls.
where g is the acceleration due to gravity. Since the vertical distance is the same fore each projectile, the time of
flight is the same for each projectile.
Setup
1. Clamp two Projectile Launchers adjacent to
each other on a sturdy table. Mount the
Launchers near one end of the table with the
Launchers aimed away from the table so the
balls will land on the floor.
2. Adjust the angle of the Launcher to 0° so
the balls will fire horizontally.
Procedure
1. Put a plastic ball into each Launcher. Cock one Launcher to the short range setting and clock the other
Launcher to the long range setting.
2. Ask the class to be quiet and listen for the balls striking the floor.
• NOTE: If there is only one click, that means that the balls hit the floor simultaneously.
3. Put both trigger release strings in the same hand and pull them at the same time so that the balls are launched
simultaneously.
4. After the balls hit the floor, ask the class if they heard one click or two.
Item
Projectile Launcher (2) and plastic ball (2)
t
2y
g
------ =
y
x
short
x
long
υ
0(long)
υ
0(short)
Figure 9.1: Shots fired simultaneously