Why a minibus is more likely to topple over when the roof rack is heavily loaded than when the roof rack is empty?

Try a turn, look at

Ac = v^2/R
needs side force from road at bottom
moment about CG is balanced by light force up on inner tires and heavy force up on outer tires. The higher the CG, the longer that moment arm.
When v^2/r is high enough, inner tires lift off road.

this is when the roof rack is heavily loaded because of the tilting bus is increasingly smaller. as the base size reduces in size, the action line of the weight of the bus moves closer to the edge about which the bus is tilted.

A minibus is more likely to topple over when the roof rack is heavily loaded compared to when it is empty due to changes in the minibus's center of gravity.

The center of gravity (CoG) is the point where the entire weight of an object is concentrated. In a minibus, the CoG is typically low, meaning most of its weight is closer to the ground. This low CoG provides stability to the vehicle, making it less prone to tipping over.

When a roof rack is heavily loaded, it increases the weight carried on top of the minibus. This additional weight raises the center of gravity of the entire vehicle. As a result, the overall stability of the minibus decreases as the CoG moves higher.

To understand the concept, you can try the following experiment:

1. Take a small empty box and place it on a flat, stable surface. This represents a minibus.
2. Observe the stability of the box when you push it from different sides. You will notice that it remains relatively stable.
3. Now, place a few heavy objects, such as books or weights, on top of the box. This represents a heavily loaded roof rack.
4. Repeat step 2 and observe the stability of the box. You will notice that it is less stable, and it may be easier to topple over when pushed.

Applying this principle to a minibus, as the weight on the roof rack increases, the vehicle's CoG rises, making it more susceptible to tipping over during sharp turns, sudden maneuvers, or when encountering strong winds.

To summarize, a minibus is more likely to topple over when the roof rack is heavily loaded because the additional weight raises the vehicle's center of gravity, reducing its stability.

Because the center of gravity is higher on the roof thus making the bus unstable