PASCO ME-6815 PROJECTILE CATCHER ACCESSORY - Manual (Page 20)

Projectile Catcher Accessory 012-05091E
16
Elastic Collision
CAUTION! DO NOT LOOK DOWN BARREL! CAUTION! DO NOT LOOK DOWN BARREL!
CAUTION! DO NOT LOOK DOWN THE BARREL.
LONG RANGE MEDIUM RANGE SHORT RANGE
Position of Ball
Launch
SHORT RANGE PROJECTILE LAUNCHER ME-6800
Yellow Band in Window Indicates Range. 9 0 8 0 7 0 6 0 5 0 4 0 3 0 2 0 1 0 0
WEAR SAFETY GLASSES WHEN IN USE.
Use 25 mm
balls ONLY!
CAUTION! DO NOT LOOK DOWN BARREL! CAUTION! DO NOT LOOK DOWN BARREL!
CAUTION! DO NOT LOOK DOWN THE BARREL.
LONG RANGE MEDIUM RANGE SHORT RANGE
Position of Ball
Launch
SHORT RANGE PROJECTILE LAUNCHER ME-6800
Yellow Band in Window Indicates Range. 9 0 8 0 7 0 6 0 5 0 4 0 3 0 2 0 1 0 0
WEAR SAFETY GLASSES WHEN IN USE.
Use 25 mm
balls ONLY!
Before Collision
Figure 3.2: Conservation of Momentum in the Elastic Collision
v = o
After Collision
m
c
m
b
v
o v
c
- v
b
m
b
m
c
The ball is launched horizontally and bounces off the catcher bumper on the cart. See
Figure 3.2.
Momentum is conserved during the collision:
P
before
= P
after
where m
b
is the mass of the ball, v
o
is the muzzle velocity of the ball, m
c
is the mass of
the catcher and cart, v
c
is the speed of the cart immediately after the collision, and v
b
is
the speed of the ball immediately after the collision. In an elastic collision, kinetic
energy is also conserved in the collision.
1
2
m
b
v
o
2 = 1
2
m
b
v
b
2 + 1
2
m
c
v
c
2
Solving the momentum equation for v
b
gives
Solving for v
c
gives
which is twice the final cart speed found for the inelastic collision.
m
b
v
0
= m
b
v
b
+m
c
v
c
v
c
=
m
b
m
b
+ m
c
v
0
v
b
= v
0
–
m
c
m
b
v
c