BeginnerTopic 15 of 106Engineering Mechanics
Centre of gravity and centroid
The point where weight or area can be considered concentrated.
In depth
The centre of gravity is where the weight acts, the centroid where area or volume is balanced. For composites x̄=Σ(Aᵢx̄ᵢ)/ΣAᵢ. Symmetry axes pass through the centroid. Holes are treated as negative areas.
Key points
- Centroid of triangle at h/3 from the base
- Semicircle at 4r/3π from the diameter
- Used for stability and bending axes
ExampleThe centroid of an L-shape is found by splitting it into two rectangles.
What is Centre of gravity and centroid?
The point where weight or area can be considered concentrated.
Why is it important to understand centre of gravity and centroid?
The centre of gravity locates where weight acts, so it decides stability against tipping and the point where a body balances.
What is the difference between centre of gravity and centroid?
They coincide for uniform density. The centroid is a purely geometric property of a shape, while the centre of gravity depends on how weight is distributed.
How does a low centre of gravity help a vehicle?
It lowers the tipping limit on a slope and reduces roll in turns, which is why racing cars and buses are designed low.
How is Centre of gravity and centroid used in practice?
Typical applications include finding where to place the counterweight on a forklift, checking whether a tall machine will tip on a slope and locating the balance point of a drone frame.
What should I learn before Centre of gravity and centroid?
Study "Method of sections" first (topic 14 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
What are the key points of Centre of gravity and centroid?
Centroid of triangle at h/3 from the base. Semicircle at 4r/3π from the diameter. Used for stability and bending axes.
Can you give an example of Centre of gravity and centroid?
The centroid of an L-shape is found by splitting it into two rectangles.
What comes after Centre of gravity and centroid?
The next topic is "Distributed loads", which builds directly on this one.
How difficult is Centre of gravity and centroid?
It is classed as Beginner in Engineering Mechanics (topic 15 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.