Centre of Mass

The diagram shows an L-shaped piece of card suspended freely from a pin at \(B\).
When the card is pushed, it swings and then comes to a stop in the position shown.
At which labelled point is the centre of mass of the card?

The diagrams show four solid cones. The centre of mass of each cone is marked by a point labelled \(M\).
Which cone is the most stable?

A heavy truck on wheels has a platform attached to it.
A man stands on the platform.
The truck does not fall over.
Which position A, B, C or D could be the centre of mass of the whole system (truck, platform and man)?

The diagram shows a uniform, flat metal sheet hanging freely from a nail at point \(\mathbf{A}\). A weight also hangs freely on a string tied to \(\mathbf{A}\).
One of the labelled points is at the centre of mass of the metal sheet.
Which point is at the centre of mass?

Passengers are not allowed to stand on the upper deck of double-decker buses.

                             
Why is this?

The lamp in the diagram is not very stable and falls over easily.

                         
Which row shows changes that would definitely make the lamp more stable?

\[
\begin{array}{|c|c|c|}
\hline & \text { base } & \text { centre of gravity } \\
\hline \text { A } & \text { narrower } & \text { higher } \\
\text { B } & \text { narrower } & \text { lower } \\
\text { C } & \text { wider } & \text { higher } \\
\text { D } & \text { wider } & \text { lower } \\
\hline
\end{array}
\]