Mission MC7 Momentum Conservation Analysis
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A 110-kilogram linebacker moving east at 3.2 m/s collides head on with a 92-kg running back moving west at 6.9 m/s. After the collision, the two players move west at 1.4 m/s. Fill in the momentum table and determine if momentum is conserved (within 1 percent). (Use the notation that east is the positive direction and west is the negative direction.)
(Note: Your numerical values are selected at random and likely different from the numbers listed here.)
The momentum (p) of an object can be calculated from knowledge of its mass (m) and velocity (v) using the formula:
p = m • v
The ultimate goal of this analysis is to determine if momentum is conserved by the collision. The following strategy will prove effective.
- Since the mass and the velocity of each car is given for before and after the collision, the momentum values can be calculated (see Formula Frenzy section).
- The total momentum of the system is simply the sum of the individual momentum values of the two cars. Once individual values have been calculated, the total momentum of the system can be calculated.
- Finally, a comparison of the pre-collision system momentum and post-collision system momentum reveals whether or not momentum is conserved. Momentum is said to be conserved if the system possesses the same amount of total momentum before the collision as after the collision (or at least within 1%).
Momentum as a Vector:
Momentum is a vector and it has a direction. The direction of an object's momentum is in the same direction that the object is moving. An eastward moving player has an eastward momentum (+); a westward moving car player a westward momentum (-).
Momentum is a vector and it has a direction. The direction of an object's momentum is in the same direction that the object is moving. An eastward moving player has an eastward momentum (+); a westward moving car player a westward momentum (-).
- How can mass and speed (or velocity) information be used to determine the momentum of an individual object?
- How can the total momentum of a system of two objects be determined?
- Is the direction that an object is moving important to the determination of its momentum?
- How can one determine if momentum is conserved by a system of two objects if pre- and post-collision mass and speed (or velocity) information is known for both objects?