US military troops come in active-duty, Guard, and reserve forces. Here's what each one does.
US military forces do a lot at home and abroad, but the different types of troops and the rules for each can be confusing.
BBC4y
Polymers - AQA Forces and stresses
Forces act on materials all the time - even if a material appears stationary it still has a force acting on it. There are five terms used to describe what type of force can act on a material: ...
BBC12mon
Timber-based materials - AQA
Forces act on materials all the time - even if a material appears stationary it still has a force acting on it. There are five terms used to describe what type of force can act on a material: ...