Qwestrum Engineering360 · Industrial & Production · Work Study & Ergonomics
Motion Economy
Motion economy reduces unnecessary body movement so each cycle becomes faster and less tiring.
Exam tip: keep SI units consistent end-to-end, write the governing relation symbolically before substituting, and sanity-check magnitude and sign.
Key formulas & points
Skim these first — then read the full notes below.
- Gilbreth motion study foundation
- Reduce unnecessary movements in layout
- Two-handed charts balance left-right work
Topic details
Introduction
Motion economy principles convert qualitative observations into practical workstation improvements. Groover and Buffa explain these principles as low-cost improvements with high cumulative impact.
Key relations & formulas
Formulas (Indian textbook notation)
Formulas (Indian textbook notation)
Formulas (Indian textbook notation)
Notation and sign conventions
Relation 1 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Industrial Engineering & Management — O.P. Khanna before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 2 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Industrial Engineering & Management — O.P. Khanna before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 3 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Industrial Engineering & Management — O.P. Khanna before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Concept in depth
Using therbligs, analysts identify ineffective search, hold, and transport motions. Two-handed process charts reveal imbalance and idle micro-time on one hand. Good industrial answers connect motion savings with reduced cycle time variability and better quality consistency, as highlighted in Chase operations strategy.
Assumptions and validity limits
State assumptions explicitly before using any relation for motion economy — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.
Wrong assumptions invalidate the entire solution even when the formula is correct. In Work Study viva and GATE descriptive questions, listing valid assumptions often earns separate marks.
Step-by-step problem approach
1. Read the question and list given data with SI units (common in Work Study papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to motion economy.
4. Use equation 1:
5. Use equation 2:
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to motion economy.
4. Use equation 1:
.
5. Use equation 2:
.
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.
Applications & exam relevance
Motion Economy appears in line balancing and productivity. In Indian industrial curricula this topic is tested because it connects theory to method study and time standards.
GATE and semester exams often combine motion economy with earlier units — revise prerequisites before attempting mixed problems.
Industry interview panels sometimes ask: "Where did you use motion economy?" — answer with a lab, mini-project, or plant visit example if possible.
Common mistakes in exams
Common mistakes include listing therbligs without classifying productive vs non-productive motions. Many also ignore eye movement and material placement angles.
Quick revision checklist
Before attempting motion economy problems, confirm you can:
1. Gilbreth motion study foundation
2. Reduce unnecessary movements in layout
3. Two-handed charts balance left-right work
2. Reduce unnecessary movements in layout
3. Two-handed charts balance left-right work
Revise the solved examples in Industrial Engineering & Management — O.P. Khanna and one previous-year GATE or university paper for this unit.
Worked examples
Try the problem first — open the solution when you are ready to check.
Cycle-time reduction by motion simplification
Problem
A task has 24 s cycle time. Motion redesign eliminates 5 s of unnecessary hand travel. Find new output per hour.
Solution
New cycle time = 24 - 5 = 19 s. Output per hour = 3600 / 19 = 189.47, so about 189 units/hour (earlier 150 units/hour).
Conceptual check — Motion Economy
Problem
In a Work Study semester or GATE paper you are asked: "State the main assumption, the governing relation, and one practical consequence of motion economy." What should a complete answer include?
📖 Standard books (India)
Industrial Engineering & Management — O.P. Khanna
Read: Syllabus unit
Work study, PPC, and OR basics
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