⚡ Quick Revision: Quick Definitions & Core Terms
Simple machines do not remove work; they make work easier by changing force, direction or distance.
Simple Machine = Effort Helps Move Load
- Symbols: Effort = force applied; Load = object moved
- SI Unit: Effort and load are forces, so unit = newton (N)
In simple machine questions, load and effort are forces. Write them in newton (N).
Load is the object to be moved vs effort is the force applied to move it.
L-E-F
Load is lifted, Effort is applied, Fulcrum is fixed.
| Term | Quick Meaning | Example |
|---|---|---|
| Machine | Makes work easier | 🔥 Scissors |
| Load | Object moved | Heavy box |
| Effort | Force applied | Pushing force |
| Fulcrum | Fixed turning point | Support of seesaw |
Do not write that machines reduce the total work to zero. Machines only make work easier.
Simple Machine = Effort Used to Move Load
- Use: To identify load and effort in machine examples.
- Unit: Load and effort = newton (N).
- A machine makes work easier.
- A simple machine has few or no moving parts.
- Load is the object to be moved.
- Effort is the force applied.
- Fulcrum is the fixed turning point of a lever.
⚡ Quick Revision: Mechanical Advantage & Formulae
Mechanical advantage has no unit because it is a ratio of two forces.
MA = Load / Effort
- Symbols: MA = mechanical advantage, Load = force overcome, Effort = force applied
- SI Unit: No unit; load and effort are measured in newton (N)
Load = MA x Effort
- Symbols: Load = resistance moved, MA = mechanical advantage, Effort = applied force
- SI Unit: Load = newton (N)
Write formula first: MA = Load / Effort. Cancel N and write MA without unit.
If load = 40 N and effort = 10 N, then MA = 40 / 10 = 4. The machine multiplies effort 4 times.
Load is the force moved by the machine vs effort is the force applied by us.
MA = L over E
Mechanical Advantage = Load divided by Effort.
| Quantity | Formula / Unit | Exam Point |
|---|---|---|
| Mechanical Advantage | MA = Load / Effort | 🔥 No unit |
| Load | Load = MA x Effort | Unit = N |
| Effort | Effort = Load / MA | Unit = N |
Do not write unit for MA. Since MA = N / N, the units cancel.
MA = Load / Effort
- Use: To find how many times a machine multiplies effort.
- Unit: No unit.
- Mechanical advantage tells how much a machine multiplies effort.
- MA = Load / Effort.
- Load and effort are measured in newton.
- Mechanical advantage has no unit.
- Higher MA means less effort is needed for the same load.
⚡ Quick Revision: Lever and Its Classes
Levers are classified according to the position of fulcrum, load and effort.
Class of Lever = Position of F, L and E
- Symbols: F = fulcrum, L = load, E = effort
- SI Unit: Load and effort are measured in newton (N)
For lever questions, first mark F, L and E. The middle one decides the class.
First class has fulcrum in middle vs second class has load in middle.
1-F, 2-L, 3-E
Class 1 has Fulcrum in middle, Class 2 has Load in middle, Class 3 has Effort in middle.
| Lever Class | Middle Position | Example |
|---|---|---|
| First Class Lever | Fulcrum in middle | 🔥 Seesaw, scissors |
| Second Class Lever | Load in middle | Wheelbarrow, nutcracker |
| Third Class Lever | Effort in middle | Tweezers, human forearm |
Do not classify a lever by shape. Classify it by the position of fulcrum, load and effort.
1st Class = F in Middle
2nd Class = L in Middle
3rd Class = E in Middle
- Use: To classify levers quickly.
- Unit: Load and effort = newton (N).
- A lever is a rigid bar turning about a fulcrum.
- First class lever has fulcrum in the middle.
- Second class lever has load in the middle.
- Third class lever has effort in the middle.
- Class of lever depends on positions of F, L and E.
⚡ Quick Revision: Other Simple Machines
Pulley, wheel and axle, inclined plane, wedge and screw are common simple machines.
Simple Machine → Less Effort / Direction Change
- Symbols: Effort = force applied; Direction change = force applied in easier direction
- SI Unit: Effort is measured in newton (N)
When force is involved in any simple machine, write the force in newton (N).
Inclined plane helps move loads upward vs wedge cuts or splits materials.
P-W-I-W-S
Pulley, Wheel and axle, Inclined plane, Wedge, Screw.
| Simple Machine | Main Use | Example |
|---|---|---|
| Pulley | Lifts load easily | 🔥 Well pulley, flag pole |
| Wheel and Axle | Helps movement or turning | Door knob, bicycle wheel |
| Inclined Plane | Moves load to height | Ramp, slide |
| Wedge | Cuts or splits | Knife, axe |
| Screw | Holds or lifts | Screw nail, jar lid |
Do not write that a screw is only a nail. A screw is an inclined plane wound around a cylinder.
Simple Machines → Make Work Easier
- Use: To remember the purpose of all simple machines.
- Unit: Effort and load are measured in newton (N).
- A pulley helps lift loads.
- Wheel and axle helps movement or turning.
- Inclined plane helps move loads to a height.
- Wedge is used for cutting or splitting.
- Screw is an inclined plane wrapped around a cylinder.
⚡ Quick Revision: Applications & Numerical Readiness
A simple machine may reduce effort, change direction of force or increase speed/distance.
MA = Load / Effort
- Symbols: MA = mechanical advantage, Load = force moved, Effort = force applied
- SI Unit: MA has no unit; load and effort = newton (N)
Effort = Load / MA
- Symbols: Effort = force applied, Load = resistance, MA = mechanical advantage
- SI Unit: newton (N)
For MA sums: write formula, substitute load and effort in N, then cancel units. Final MA has no unit.
If load = 60 N and effort = 20 N, then MA = 60 / 20 = 3. The machine multiplies effort 3 times.
Reducing effort means less force needed vs changing direction means force is applied in a different direction.
R-D-S
Simple machines Reduce effort, change Direction or increase Speed.
| Application | How It Helps | Example |
|---|---|---|
| Reducing Effort | Less force needed | 🔥 Wheelbarrow |
| Changing Direction | Effort applied in easier direction | Pulley |
| Moving to Height | Load moved up gradually | Ramp |
| Cutting/Splitting | Force concentrated at edge | Knife, axe |
Do not give unit for mechanical advantage. Load and effort have units, but MA has no unit.
MA = Load / Effort
Effort = Load / MA
- Use: Simple mechanical advantage numericals.
- Unit: MA has no unit; effort and load = N.
- Simple machines make work easier.
- They may reduce effort or change force direction.
- MA = Load / Effort.
- Mechanical advantage has no unit.
- Load and effort are measured in newton.
⚡ Quick Revision: Final Recall Sheet & Exam Readiness
A simple machine makes work easier by reducing effort, changing direction of force or increasing speed/distance.
MA = Load / Effort
Effort = Load / MA
Load = MA x Effort
- Symbols: MA = mechanical advantage, Load = resistance, Effort = applied force
- SI Unit: Load and effort = newton (N); MA has no unit
For MA numericals, divide load by effort and cancel N. Final MA has no unit.
| Topic | Must Remember | Example |
|---|---|---|
| Simple Machine | 🔥 Makes work easier | Lever, pulley |
| Lever | Rigid bar turning about fulcrum | Seesaw, scissors |
| Pulley | Helps lift load or change direction | Flag pole pulley |
| Inclined Plane | Sloping surface for lifting load | Ramp |
| MA | Load / Effort | No unit |
Load is the resistance moved vs effort is the force applied.
Do not write newton as the unit of mechanical advantage. MA has no unit.
L-E-F + P-W-I-W-S
Load, Effort, Fulcrum + Pulley, Wheel and axle, Inclined plane, Wedge, Screw.
Simple Machine → Load + Effort → Easier Work → Mechanical Advantage → MA = Load / Effort
MA = Load / Effort
- Use: To find how much a machine multiplies effort.
- Unit: No unit.
- Simple machines make work easier.
- Load is the resistance moved by a machine.
- Effort is the force applied to move the load.
- MA = Load / Effort.
- Mechanical advantage has no unit.