Simple machines questions appear in every single Grade 7 Integrated Science examination. The most common questions show a picture of an everyday tool (like a wheelbarrow, pair of scissors, or bottle opener) and ask: "Which class of lever is shown?" Memorize the FLE 1-2-3 secret rule below and you will get every question right!
Help your child explore simple machines around the home: ask them to point out where the pivot, effort, and load are located on everyday items such as kitchen scissors, nutcrackers, door handles, and can openers.
Table of Contents
- 1. What is a Simple Machine? (Effort, Load & Fulcrum)
- 2. The Three Classes of Levers (The FLE 1-2-3 Rule)
- 3. Pulley Systems: Fixed, Movable & Block and Tackle
- 4. Other Simple Machines: Inclined Plane, Wedge, Wheel & Axle, Screw
- 5. Friction in Machines & The Role of Lubricants
- 6. Grade 7 Past Examination Sample Questions
- 7. Frequently Asked Questions
1. What is a Simple Machine?
A simple machine is a device that makes work easier by allowing a smaller force (effort) to move a larger force (load), by changing the direction of the force, or by increasing the speed at which work is done.
The Three Key Terms Every Candidate Must Know:
- Load: The heavy object or resistance force being lifted, cut, or moved.
- Effort: The force applied by human muscles or a motor to overcome the load.
- Fulcrum (or Pivot): The fixed turning point about which the lever rotates.
2. The Three Classes of Levers (The FLE 1-2-3 Rule)
A lever is a rigid bar that turns around a fixed point called a fulcrum. Levers are classified based on the relative position of the Fulcrum, Load, and Effort:
The Golden Rule: FLE = 1 - 2 - 3
Remember what is positioned IN THE MIDDLE:
• F in the middle = 1st Class Lever
• L in the middle = 2nd Class Lever
• E in the middle = 3rd Class Lever
| Class of Lever | Position of Parts | Everyday Examples Tested in ECZ Exams |
|---|---|---|
| First Class Lever (1) | Fulcrum is in the middle (between Effort and Load). | Seesaw, pair of scissors, pliers, claw hammer removing a nail, crowbar. |
| Second Class Lever (2) | Load is in the middle (between Fulcrum and Effort). | Wheelbarrow, bottle opener, nutcracker, paper guillotine. |
| Third Class Lever (3) | Effort is in the middle (between Fulcrum and Load). | Tweezers, sugar tongs, fishing rod, human forearm, broom. |
3. Pulley Systems: Fixed, Movable & Block and Tackle
A pulley is a grooved wheel around which a rope or cable passes. In Zambian primary exams, three types of pulleys are tested:
Single Fixed Pulley
The axle is firmly attached to a ceiling, beam, or flagpole.
- Effort = Load.
- Does not multiply force.
- Advantage: Changes the direction of force (pull down to lift up).
Movable Pulley
The pulley wheel moves along with the load.
- Cuts the required effort by half (Effort = $\frac{1}{2}$ Load).
- Multiplies force.
- Effort moves twice as far as the load.
Block and Tackle
A combination of fixed and movable pulleys working together.
- Used in cranes, construction sites, and vehicle breakdown tow trucks.
- Lifts very heavy loads with very small human effort.
4. Other Simple Machines: Inclined Plane, Wedge, Wheel & Axle, Screw
Candidates should know the practical applications of all six fundamental simple machines:
| Machine | How It Works | Practical Examples |
|---|---|---|
| Inclined Plane (Ramp) | A sloping surface connecting a lower level to a higher level; trades distance for reduced effort. | Sloping ramp used to push oil drums into a truck; wheelchair ramps; staircase; winding mountain roads. |
| Wedge | Two inclined planes placed back to back; used to split, cut, or pierce materials. | Axe blade, knife, nail, chisel, chisel tip of a plough share. |
| Wheel and Axle | A large wheel connected to a smaller central shaft (axle); turning the wheel turns the axle with greater force. | Steering wheel, doorknob, bicycle pedals, windlass winch at a village well. |
| Screw | An inclined plane wrapped spirally around a central cylinder (threads). | Wood screw, bolt and nut, screw jack lifting a car, bottle cap. |
5. Friction in Machines & The Role of Lubricants
Friction is the opposing resistance force that occurs when two surfaces slide against each other. In simple machines, friction produces unwanted heat and wears out moving parts, making machines less efficient.
Methods to Reduce Friction in Machines:
- Lubrication: Applying oil or grease between metal contact surfaces (e.g., greasing bicycle chains and cart axles).
- Ball Bearings & Rollers: Replacing sliding friction with rolling friction.
- Smoothing / Polishing: Smoothing rough mechanical surfaces.
6. Grade 7 Past Examination Sample Questions
A boy uses a wheelbarrow to carry bags of cement. Which of the following is correct about a wheelbarrow?
A. The fulcrum is in the middle.
B. The load is between the fulcrum and the effort.
C. The effort is between the fulcrum and the load.
D. It is a third class lever.
Answer: B (The wheel is the fulcrum at one end, the hands apply effort at the handles, and the cement load is in the middle. Therefore, it is a 2nd class lever).
Which simple machine is used on top of a school flagpole to raise the Zambian national flag?
A. Inclined plane B. Screw C. Single fixed pulley D. Wedge
Answer: C (A single fixed pulley changes the direction of pull so you pull downward while the flag rises upward).
7. Frequently Asked Questions
Why can't a machine ever be 100% efficient?
No machine is 100% efficient because some input energy is always lost as heat and sound energy due to internal friction between moving parts.
Is a pair of scissors one lever or two?
A pair of scissors is a double first-class lever connected at a common central pivot (the screw or pin).
What is the advantage of using an axe instead of a flat piece of iron to chop firewood?
An axe blade is a wedge that concentrates the applied swing force onto a very sharp, thin cutting edge, generating high pressure to split wood fibers apart.