Unit 5 Physics - C2 + C3

Equations

Density = mass / volume

Tensile stress = Force / Area

Tensile strain = extension / original length = ratio

Youngs modulus = Stress / Strain

Spring Force = Spring constant * extension or compression

Density - the amount of mass you have in a certain volume. Solids are usually more dense than liquids and liquids are usually more dense than gasses.

Elasticity

The ability of a material to bounce back to its original shape after being deformed.

Elastic materials have a limit of elasticity which is where the material is stretched too much and it is unable to fully return to its original shape

Elastic materials when stretched have had work done on them. This is then stored in something called an elastic store. When the elastic material is released all energy in the elastic store gets transferred into kinetic energy and thermal. This is how a sling shot works.

Materials

Tensile stress - how much force is applied per unit of cross sectional area

Tensile Strain - Fractional change in the original length of the wire

Stress is directly proportional to strain. --> the ratio of stress to strain is known as the Youngs Modulus ...

The bigger the Youngs Modulus is the stiffer that material is

Yield Point - the point at which a material takes on too much stress and hits the elastic limit.

Creep - Slow deformation when a material is under constant mechanical stress

Fluids in motion

Laminar flow: image

Turbulent flow: image

Flow has to push particles at a constant rate. So if there is an obstruction that separates the flow to two paths which are under different conditions like pressure and or area the flow will speed up to compensate for this.

Wings work due to speeds of the air above the wing travelling faster to compensate for the longer distance its got to travel with the air below. This means pressure below the wing is stronger then the pressure above and more force is being pushed up causing lift. This is due to Bernoulli's principle

Viscosity - the resistance of a liquid to flow. The higher the viscosity levels of the liquid are the more resistance its going to have to flow.

Viscosity is effected by both Temperature and Pressure

Bernoulli's principle - when an incompressible, smoothly flowing fluid gains speed, the internal pressure of the fluid decreases and when the fluids speed decreases, internal pressure increases.

Non-Newtonian fluid - viscosity varies depending on the force applied to it.