Key Takeaways

  • Pressure, buoyancy, density, current flow, and basic circuits are common mechanical-comprehension themes.
  • Hydraulic systems multiply force because pressure is transmitted through a fluid.
  • In basic electricity, current needs a complete path, and greater resistance reduces current when voltage is unchanged.
  • Motion questions often reduce to inertia, acceleration, gravity, and balanced versus unbalanced forces.
  • You do not need engineering depth; you need clean first-principles reasoning under time pressure.
Last updated: March 2026

Fluids, Electricity, and Motion

Fluids

Pressure

Pressure is force spread over area.

  • Same force on smaller area = greater pressure
  • Same force on larger area = less pressure

That is why a sharp point penetrates better than a blunt one.

Hydraulics

Hydraulic systems use fluid pressure to transfer force. A larger output piston can produce a larger output force, though it moves a shorter distance.

Density and Buoyancy

PrincipleResult
Object less dense than fluidFloats
Object more dense than fluidSinks
More displaced fluidGreater buoyant force

Electricity

You do not need advanced circuit math for most basic questions. You do need the relationships.

ConceptKey Idea
VoltageElectrical push
CurrentFlow of charge
ResistanceOpposition to current
Closed circuitComplete path, current can flow
Open circuitBroken path, current stops

Practical Rules

  • More resistance usually means less current if voltage stays the same.
  • A dead battery or broken wire can open the circuit.
  • Conductors allow current to move easily; insulators resist current flow.

Motion

Newton-style basics

SituationMeaning
Object at rest stays at rest unless acted onInertia
Unbalanced force presentMotion changes
Balanced forcesNo change in motion
Gravity acts downwardObjects accelerate downward when unsupported

A Good MCT Habit

When you miss a mechanical question in practice, do not just memorize the answer. Ask:

  • What physical relationship did I miss?
  • Was it force, pressure, rotation, resistance, or motion?

That review habit improves mechanical reasoning much faster than rereading definitions.

Test Your Knowledge

If the same force is applied over a smaller area, what happens to pressure?

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Test Your Knowledge

What is required for current to flow in a simple electrical circuit?

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Test Your Knowledge

If forces on an object are balanced, what happens to its motion?

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