AHA! Physics Moments- Mastering U-Tube Manometer in SPM Physics: Formulas & 3 Cases Explained

SPM Physics Form 5 Pressure: How to Solve U-Tube Manometer (P_gas) Questions Easily!

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Case (a): Balanced Pressure

• (i) P_gas = P_atm
• (ii) Compare gas pressure with atmospheric pressure:
  P_gas = P_atm

💡 SPM Exam Tip: When both liquid levels are equal, there is no pressure difference. Gas pressure equals atmospheric pressure perfectly!

Case (b): Gas Pressure Less Than Atmospheric Pressure

• (i) P_gas = P_atm - h
• (ii) Compare gas pressure with atmospheric pressure:
  P_gas < P_atm

💡 SPM Exam Tip: Gas side level is higher? That means the gas is weaker than the atmosphere! Always subtract the height difference (h):
P_gas = P_atm - h.

Case (c): Gas Pressure Greater Than Atmospheric Pressure

• (i) P_gas = P_atm + h
• (ii) Compare gas pressure with atmospheric pressure:
  P_gas > P_atm

💡 SPM Exam Tip: Gas side level is lower (pushed down)? The gas is stronger! Always add the height difference (h):
P_gas = P_atm + h.

💡 "Not by sight, but by insight."

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