Shopping carts (also known as shopping trolleys or shopping baskets in some parts of the world) are a great example of a simple machine at work. They consist of only two main parts: a metallic basket and a set of wheels. The basket has a handle attached to it (which helps in steering the cart), and it’s installed above a set of four small wheels that make pushing, pulling and steering the cart very convenient.
It’s quite clear that a shopping cart consists of very simple components, but it is of tremendous assistance to shoppers while they roam throughout the shopping mart looking for a particular flavor of cookie or a big bottle of anti-dandruff shampoo.
In some countries, including India, the United Kingdom and Australia, there is a rather queer problem with trolleys; they seem to have a mind of their own! Suppose you try to turn a trolley towards, say, the left. It would definitely turn, but not towards the left; it would either go towards the right or move straight ahead. The same thing happens when you push them in the forward direction; it goes left or right unless you apply a surprisingly large amount of force to move it in the desired direction.
Picture Credit : Google