Physics Momentum “Bucket” Model - thecubscientist.com

Step 3: Draw Momentum Buckets
The concept of Conservation of Momentum requires the student to analyze the
INSTANT BEFORE the collision and the INSTANT AFTER the collision. Here students
fill each “momentum bucket” depending on whether or not each object is
moving (i.e. possesses momentum). There are three possible cases. Each is
described below:
Case I: One or both objects are traveling in the positive direction BEFORE the
collision; one or both objects is traveling in the positive direction AFTER the
collision. In the case shown below, both m1 and m2 are traveling to the right
before the collision, only m2 is moving after the collision.
Before collision
After collision
v1i v2i v2f
m1 m2 m1
m2
+
= +
pm1
in
pm2
pm2
The “i” and “f” subscripts represent the “initial” and “final”, representing the
instant before and after the collision, respectively.
m1 = the mass of object 1 [kg]
v1i = the velocity of object 1 at the instant BEFORE the collision [m/s]
v1f = the velocity of object 1 at the instant AFTER the collision [m/s]
m2 = the mass of object 2 [kg]
v2i = the velocity of object 2 at the instant BEFORE the collision [m/s]
v2f = the velocity of object 2 at the instant AFTER the collision [m/s]
p = the momentum of the object [kg m/s]
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Physics | Loyola High School