Imagine trying to pour a very thick (non-Newtonian) fluid like molasses out of a container. You might expect the molasses to pour out slowly, but instead it flows out quickly and evenly. This is because non-Newtonian fluids don't follow Newton's laws of viscosity, which state that a fluid's resistance to flow is proportional to the applied force. Instead, non-Newtonian fluids like molasses have a low resistance to flow when there is low shear force and a high resistance to flow when there is high shear force. This means that non-Newtonian fluids can be both viscous (thick) and elastic (stretchy).
There are many everyday examples of non-Newtonian fluids, including blood, ketchup, custard, and whipped cream. These materials have all sorts of interesting applications in product development. For example, non-Newtonian fluids can be used to create shatter-proof glass and bulletproof vests. They can also be used in 3D printing and as sealants for wounds. As research into non-Newtonian fluids continues, we are likely to find even more uses for these fascinating materials.