Lesson 6: Relativistic Momentum
The physics of subatomic particles involves the collision of particles travelling at relativistic speeds so it is important to address relativistic momentum. We use something called the rest mass in the formula for relativistic momentum and this mass is measured either using Newton's second law in Newtonian physics or gravitationally. The inertial and gravitational masses are the same for slow-moving objects but for accelerated particles travelling at high speeds, one must use rest mass.
The focus of this chapter is on the idea of rest mass and when and how to use the formula for relativistic momentum.
- Able to use the formula for the relativistic momentum to understand the relativistic momentum increases as the speed increases.
- Knowing that the rest mass of an object is its mass in the inertial reference frame in which the object is at rest.
- Understanding that an object that has mass will never be able to be accelerated to the speed of light based on the formula for relativistic momentum.
It would be beneficial to start off the lesson by showing students a portion of the following video to remind them of what momentum is and conduct a quick review of this concept:
I highly encourage the use of the SMART Board for this lesson to show the derivation of the relativistic momentum formula and the idea of rest mass. Moreover, students can come up to the SMART Board to work out examples.
The video below shows how the relativistic momentum can be derived by analyzing specific situations in which its effects apply.
In order to consolidate the lesson, one suggestion is to:
- Ask students to form groups of 5 to 6.
- Assign each group a different topic that was discussed today such as rest mass, gravitational mass, Newtonian momentum and relativistic momentum.
- Have each group consolidate their concept by briefly explaining the definition and any other key information pertaining to said concept.
- Hirsch, A., Stewart, C., Martindale, D, & Barry, M. (2011). Nelson Physics 12. Toronto: Nelson Thomson Learning