Understanding Toy Rocket Physics: A Comprehensive Analysis
The physics behind toy water rockets demonstrates fascinating principles of pressure, force, and acceleration. This detailed examination breaks down the calculations and concepts from an OCR A Level Physics unified exam June 2019 question involving a water-powered toy rocket system.
Definition: A water rocket operates on Newton's Third Law, using pressurized air to expel water, creating thrust that propels the rocket upward.
When analyzing the rocket's initial conditions, we find a 1.5-liter plastic bottle containing 0.30 liters of water and 1.2 liters of trapped air at 17°C. The air is pressurized to 2.4 × 10⁵ Pa before launch. Calculating trapped air moles in toy rocket requires applying the ideal gas equation PV = nRT, where the volume is 1.2 × 10⁻³ m³ and temperature is 290K, yielding 0.12 moles of trapped air.
The pressure dynamics follow Boyle's Law as the water exits. Using P₁V₁ = P₂V₂, we can determine that the final pressure just before water depletion is 1.9 × 10⁵ Pa. This pressure difference between the trapped air and atmosphere creates the thrust necessary for lift-off.