GCSE Physics: Moments, Pressure and Terminal Velocity

This material covers the parts of the GCSE Physics forces topic that go beyond resultant forces, Newton's laws and stopping distances. Moments, pressure in fluids and terminal velocity are separate (triple) physics content, for example in AQA's specification, and pressure due to a column of liquid and upthrust are Higher tier there. The equation v² − u² = 2as is used in both combined science and physics.

The first section is about turning effects. The moment of a force is the force multiplied by the perpendicular distance from the pivot, so you convert centimetres to metres before multiplying. You apply the principle of moments to a balanced see-saw, explain why a longer spanner makes a tight nut easier to undo, and describe how gears pass on a turning effect: a small gear driving a larger one makes it turn more slowly but with a larger moment.

The second section is about pressure in fluids. Pressure acts at right angles to any surface, and pressure = force ÷ area applies to a hydraulic piston. At Higher tier you calculate the pressure due to a column of liquid with p = hρg, and explain upthrust: pressure increases with depth, so the water pushes up on the bottom of a submerged object harder than it pushes down on the top. Whether the object floats or sinks depends on how its weight compares with the upthrust. You also explain why atmospheric pressure falls with height.

The third section uses v² − u² = 2as, which links speeds and distance without needing a time: the speed of a falling object after a given drop, and the braking distance of a car from its speed and deceleration. Finally you describe the fall of a skydiver: air resistance grows with speed until it balances the weight and the skydiver reaches terminal velocity; opening the parachute makes air resistance larger than the weight, so the skydiver slows to a new, lower terminal velocity.

All the equations are given on the real papers, so the questions focus on choosing and applying them. The material offers three formats. The quiz has 12 questions mixing single-answer and multiple-answer items, each with a worked explanation. The flashcards give quick revision of the equations and key ideas. The written work is a printable sheet of 8 longer questions, including a balanced-rule problem, a hydraulic jack, the pressure on a dam, braking distances at two speeds and a full description of a skydive, which you answer by hand and upload for feedback on each answer.

• Calculate moments and apply the principle of moments to balanced objects
• Explain how levers and gears transmit and change turning effects
• Use pressure = force ÷ area for fluids and (Higher) p = hρg for a liquid column
• (Higher) Explain upthrust and use it to decide whether an object floats or sinks
• Use v² − u² = 2as for falling objects and braking distances
• Describe and explain the motion of a skydiver, including terminal velocity

Practice material written by Zestly, based on the DfE GCSE physics subject content (forces: moments, levers and gears; pressure in fluids; motion equations; terminal velocity), with AQA GCSE Physics 8463 used as the example specification.