Define what is meant by the torque of a couple.
In Fig. 4.1, a wheel is held by a pin P at its centre of gravity. The wheel lies in a vertical plane and has radius $25\,\text{cm}$. Two parallel forces, each of $35\,\text{N}$, act at the rim in the vertical directions shown in Fig. 4.1. Friction between the pin and the wheel is negligible. State two other forces that act on the wheel. Give the direction of these forces and where they act.
Calculate the torque of the couple acting on the wheel.
The resultant force on the wheel is zero. Explain, by referring to the four forces acting on the wheel, how this can be the case.
State and explain whether the wheel is in equilibrium.
As shown in Fig. 4.1, a wheel is held by a pin P at its centre of gravity. Its plane is vertical and its radius is $25\,\text{cm}$. Two parallel forces, each of $35\,\text{N}$, act at the rim in the vertical directions shown in Fig. 4.1. The friction between the pin and the wheel is negligible.