Conservation Laws
Big Ideas
- Momentum is inertia in motion and is equal to the product of mass and velocity. p = m v
- Impulse causes and is equal to a change in momentum. F t = ∆ (m v)
- During a collision or explosion, the total momentum of a system of objects doesn't increase or decrease, it's conserved (as long as there's not a net external force). Therefore, the total momentum of a system of objects before a collision or explosion is always equal to the total momentum after, and the total change in momentum is always zero. m v 1 + m v 2 before = m v 1 + m v 2 afer
- Energy cannot be created or destroyed. It can be transformed from one form to another, but the total amount of energy never changes. PE + KE before = PE + KE after
- Friction and air resistance are the causes of common losses of mechanical energy in systems. They usually transform mechanical energy to thermal energy.
Standards for Learning
- C1: Use the impulse-momentum principle to design, evaluate, and refine a device that minimizes the force on an object during a collision.
- C2: Use math to support the claim that the total momentum of a system of objects is conserved.
- C3: Develop and use a model that accounts for energy in kinetic, potential, and thermal combinations.
- C4: Create a spreadsheet that is based on the Conservation of Energy principle.
- C5: Design, build, and refine a device that converts one form of energy into another form of energy.