Pressure & Pressure Differences in FluidsEdexcel GCSE Physics: Flashcards
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State the equation for pressure.
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- State the equation for pressure.
- P = F ÷ A, where P is pressure (Pa), F is force normal to the surface (N) and A is the area (m²).
- What are the units of pressure?
- Pascals (Pa), equivalent to N/m².
- Why does a sharp knife cut more easily than a blunt one, for the same force?
- A sharp knife has a much smaller contact area, so the same force produces a much greater pressure.
- How is pressure transmitted in a fluid?
- Equally in all directions throughout the fluid.
- How does a hydraulic system multiply force?
- Pressure is transmitted equally through the liquid, so a small force on a small piston area produces the same pressure that acts on a larger piston area, giving a larger output force.
- State the equation for pressure difference at depth in a liquid.
- ΔP = h × ρ × g, where h is depth (m), ρ is density (kg/m³), and g is gravitational field strength (N/kg).
- Why does pressure increase with depth in a liquid?
- Because there is more liquid, and therefore more weight, pressing down from above at greater depths.
- Does the pressure difference in a liquid depend on the shape of the container?
- No — it depends only on depth, density and gravitational field strength.
- Calculate the pressure exerted by a 20 N force acting normally on a 0.5 m² area.
- P = F ÷ A = 20 ÷ 0.5 = 40 Pa.
- What must be true about the force in P = F/A?
- It must be normal (at right angles) to the surface.
- Give an everyday example of a hydraulic system.
- A car's hydraulic braking system, or a hydraulic car jack.
- A liquid has density 1000 kg/m³. Find the pressure difference at a depth of 2 m (g = 10 N/kg).
- ΔP = h × ρ × g = 2 × 1000 × 10 = 20,000 Pa.