Investigation: conservation of linear momentum

Aim: to verify that total momentum is conserved in a collision between two trolleys.

• Apparatus: two trolleys, ticker timers or motion sensors, runway, masses.
• Method: measure the velocity of each trolley before and after the collision, and record their masses.
• Compare total p before with total p after; they should agree within experimental error.
• Also compare total kinetic energy to classify the collision as elastic or inelastic.

• Isolated system — no external net force acts.
• Experimental error — the small difference caused by friction and measurement limits.