HS-PS2-2
The standard
Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.
Next Generation Science Standards
What this standard means
Students need to use numbers, symbols, graphs, or tables to show that total momentum before an interaction equals total momentum after it. Keep the focus on two objects moving in one line, such as carts colliding or separating. They should calculate momentum using mass times velocity and track direction with positive and negative signs.
Mastery looks like setting a clear system, finding total momentum before and after, and using the math to support a claim. Students often mix up momentum and force, drop negative signs, or compare each object separately instead of the total system.
Ways to teach it
- Use two dynamics carts with different masses, motion sensors, and a track to measure velocities before and after a collision.
- Ask students to write: How can both carts change motion while the total momentum stays the same?
- Give a two-cart before-and-after velocity table and ask students to calculate total momentum on each side.
- Connect the math to a bowling ball hitting a pin, with students identifying the system and momentum transfer.
Plan a lesson for HS-PS2-2
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