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
| Principle | Result |
|---|---|
| Object less dense than fluid | Floats |
| Object more dense than fluid | Sinks |
| More displaced fluid | Greater buoyant force |
Electricity
You do not need advanced circuit math for most basic questions. You do need the relationships.
| Concept | Key Idea |
|---|---|
| Voltage | Electrical push |
| Current | Flow of charge |
| Resistance | Opposition to current |
| Closed circuit | Complete path, current can flow |
| Open circuit | Broken 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
| Situation | Meaning |
|---|---|
| Object at rest stays at rest unless acted on | Inertia |
| Unbalanced force present | Motion changes |
| Balanced forces | No change in motion |
| Gravity acts downward | Objects 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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D