What are the four types of motion, and how do mechanisms convert one into another?
The four types of motion - linear, rotary, reciprocating and oscillating - and the idea of mechanisms converting one type of motion into another.
A CCEA GCSE Technology and Design answer on the four types of motion - linear, rotary, reciprocating and oscillating - with everyday examples, and how mechanisms change the type, direction or size of a motion or force.
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What this dot point is asking
CCEA wants you to name and describe the four types of motion - linear, rotary, reciprocating and oscillating - give everyday examples of each, and understand that a mechanism can convert one type of motion into another or change its direction or size. This vocabulary underpins the whole mechanisms topic.
The answer
The four types of motion
Learn each with a clear example:
- Linear: a lift moving straight up, a paper trimmer blade, a conveyor belt section.
- Rotary: a wheel, a fan, a drill chuck, a clock hand.
- Reciprocating: a sewing-machine needle, a saw blade, a piston in an engine.
- Oscillating: a pendulum, a child's swing, a metronome arm, a windscreen wiper (it swings in an arc).
The pairs that are easy to confuse are reciprocating (straight line, to and fro) versus oscillating (arc, to and fro about a pivot). Reciprocating is in a line; oscillating is on a curve.
What a mechanism does
Mechanisms are the building blocks of moving products. A bicycle, a stapler and a car steering system are all collections of mechanisms.
Converting one motion into another
Input and output
A useful way to think about any mechanism is in terms of input (the motion or force you put in) and output (the motion or force you get out). A mechanism links the two and may change the type, direction, speed or force between them. This connects directly to the systems approach used in the electronics topics.
Worked example: identifying motions in a product
Examples in context
- Example 1. A bicycle
- The pedals and legs give reciprocating and rotary motion, the chain transfers rotary motion to the wheel (rotary output), showing transfer and conversion of motion.
- Example 2. A sewing machine
- Rotary motion of the motor is converted by a crank into the reciprocating up-and-down motion of the needle, a clear rotary-to-reciprocating conversion.
- Example 3. A metronome
- The arm oscillates in an arc about its pivot to keep musical time, a pure example of oscillating motion.
Being able to name each motion, give an example, and explain a conversion lets you answer both the "name the four types" and "what does a mechanism do" questions.
Try this
Q1. Name the four types of motion. [4 marks]
- Cue. Linear, rotary, reciprocating and oscillating.
Q2. Give an everyday example of reciprocating motion. [1 mark]
- Cue. A saw blade, a sewing-machine needle or an engine piston.
Q3. What is the difference between reciprocating and oscillating motion? [2 marks]
- Cue. Reciprocating is to and fro in a straight line; oscillating is to and fro in an arc about a pivot.
Q4. What does a mechanism do? [2 marks]
- Cue. It transfers or changes a motion or force - changing its type, direction, speed or size.
Q5. Name a mechanism that changes rotary motion into linear motion. [1 mark]
- Cue. A rack and pinion.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style4 marksName the four types of motion and give an everyday example of each.Show worked answer →
Award one mark per correct type with a valid example:
Linear: motion in a straight line, e.g. a lift moving up, or a paper trimmer blade.
Rotary: turning in a circle, e.g. a wheel or a fan.
Reciprocating: backwards and forwards in a straight line, e.g. a saw blade or a sewing-machine needle.
Oscillating: swinging backwards and forwards in an arc, e.g. a pendulum or a swing.
CCEA style3 marksWhat is a mechanism, and give one example of a mechanism that changes one type of motion into another.Show worked answer →
A mechanism is a device that transfers or changes a motion or force, often turning one type of motion into another or changing its direction or size (1).
Example: a rack and pinion changes rotary motion (the pinion gear turning) into linear motion (the rack moving in a straight line) (1), as used in a car steering system or a railway (1).
Related dot points
- Levers and linkages: the three classes of lever, the principle of moments, mechanical advantage, and linkages that change the direction of motion.
A CCEA GCSE Technology and Design answer on levers and linkages: the three classes of lever, the principle of moments with the equation moment equals force times distance, mechanical advantage, and linkages that change the direction or size of a motion.
- Gears and gear trains: simple gear trains, gear ratio, the effect on speed, torque and direction, idler gears, and compound gear trains.
A CCEA GCSE Technology and Design answer on gears and gear trains: simple gear trains, calculating gear ratio from teeth, the effect on output speed, torque and direction, the role of an idler gear, and compound gear trains for large ratios.
- Belt and pulley drives, and chain and sprocket drives: transmitting rotary motion over a distance, the velocity ratio, and choosing between them.
A CCEA GCSE Technology and Design answer on belt and pulley drives and chain and sprocket drives: transmitting rotary motion over a distance, calculating the velocity ratio from pulley or sprocket sizes, slip, and choosing between belts and chains.
- Motion converters: cams and followers, crank and slider, rack and pinion, and screw threads, and the motion change each produces.
A CCEA GCSE Technology and Design answer on motion converters: cams and followers, the crank and slider, rack and pinion, and screw threads, explaining the input and output motion each one produces and where they are used.
- The systems approach: representing electronic and control systems as input, process and output blocks, with feedback, using block (systems) diagrams.
A CCEA GCSE Technology and Design answer on the systems approach: describing an electronic or control system as input, process and output blocks, the idea of feedback, and using block (systems) diagrams to design and analyse a system.
Sources & how we know this
- CCEA GCSE Technology and Design specification — CCEA (2017)