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Simple Machines

Basic Science & Engineering · Measurement, Drawing & Mechanics

Overview

Simple machines (lever, pulley, inclined plane, wheel and axle, screw, wedge) make work easier by changing force or direction.

Key points

Lever classes: first (fulcrum in middle), second (load in middle), third (effort in middle).
Mechanical advantage MA = load ÷ effort.
Velocity ratio VR = distance moved by effort ÷ distance moved by load.
A single fixed pulley has MA = 1 (only changes direction).
Inclined plane VR = length ÷ height.

Explanation

Second-class levers always have MA > 1 (wheelbarrow, nutcracker).
Third-class levers have MA < 1 but gain speed (tongs, forearm).
A movable pulley has ideal MA = 2.
Screws are inclined planes wrapped around a cylinder.

Step by step

Identify the concept, tool or rule involved.
Recall the definition, value or procedure.
Check units, safety logic and the direction of the effect.

Examples

Effort arm 2 m, load arm 0.5 m → ideal MA = 4.
An inclined plane 5 m long and 1 m high → VR = 5.
A single fixed pulley → MA = 1.

Traps and advanced points

Trap: Confusing lever classes.
Trap: Using height ÷ length for VR.
Trap: Thinking a fixed pulley reduces effort.

Quick revision

MA = load/effort.
VR = effort distance/load distance.
Lever classes by middle element.

Practice MCQs

Concept check: A concave lens is commonly used to correct which defect?
1. Colour blindness
2. Presbyopia only
3. Hypermetropia
4. Myopia
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Answer: (d) Myopia. A concave lens is commonly used to correct Myopia.
Concept check: Frequency is measured in which unit?
1. hertz
2. newton
3. decibel
4. tesla
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Answer: (a) hertz. Frequency is measured in hertz.
Concept check: Ohm’s law relates voltage, current and what?
1. Pressure
2. Resistance
3. Mass
4. Temperature only
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Answer: (b) Resistance. Ohm’s law relates voltage, current and Resistance.
Concept check: The genetic material in most organisms is what?
1. ATP
2. Glucose
3. Cellulose
4. DNA
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Answer: (d) DNA. The genetic material in most organisms is DNA.
ALP Basic Science & Engineering: Complete the statement: “Efficiency of a machine is ____.”
1. joule
2. ultraviolet radiation
3. greenhouse gases
4. useful output/input × 100%
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Answer: (d) useful output/input × 100%. Efficiency of a machine is useful output/input × 100%. Real machines have efficiency below 100%.
ALP Basic Science & Engineering: Complete the statement: “Mechanical advantage of a machine is ____.”
1. metre
2. load/effort
3. kilogram
4. useful output/input × 100%
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Answer: (b) load/effort. Mechanical advantage of a machine is load/effort. MA compares output load to input effort.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “useful output/input × 100%”?
1. CPU stands for
2. vernier caliper is commonly used to measure
3. efficiency of a machine is
4. a strong password is improved by
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Answer: (c) efficiency of a machine is. The correct answer is “efficiency of a machine is”. Real machines have efficiency below 100%.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “load/effort”?
1. for an electrical fire, water is generally
2. an operating system mainly
3. mechanical advantage of a machine is
4. CPU stands for
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Answer: (c) mechanical advantage of a machine is. The correct answer is “mechanical advantage of a machine is”. MA compares output load to input effort.