Air Pressure• air pressure is caused by the motion of particles in the air• you do not feel the weight of the air because the pressure inside your body is equal to the air pressure
Air Pressure• air pressure changes with altitude – the higher you are, the lower the air pressure
Air Pressure• Barometer – instrument used to measure air pressure
Water Pressure• the force of water pressure on an object is the same in all directions• water pressure changes with depth – the deeper you are, the greater the water pressure
Water Pressure• Manometer – instrument used to measure pressure in a liquid
What is Bernoulli’s principle? • Bernoulli’s Principle – principle that states that as the speed of a fluid increases, its pressure decreases
Bernoulli’s Principle• airplane wings are designed to use Bernoulli’s principle – air traveling over the wings moves faster than air underneath – this reduces the pressure on top of the wing, allowing it to be pushed upward
Bernoulli’s Principle• three forces combine to help an airplane fly – the upward force on a plane’s wing is called lift – a forward force, or thrust, helps the plane take off and maintain air speed – the air resistance on a plane is called drag
Work is the transfer of energy through motion. Inorder for work to take place, a force must be exertedthrough a distance. The amount of work donedepends on two things: the amount of force exertedand the distance over which the force is applied.There are two factors to keep in mind whendeciding when work is being done: something has tomove and the motion must be in the direction of theapplied force.
Formula for WorkWork can be calculated by using the following formula: Work=force x distance J = N X m
Work is done on thebooks when they arebeing lifted, but nowork is done onthem when they arebeing held orcarried horizontally.
PowerRate at which work is performed orenergy is expended
W P= tPower equals Work divided by Time W = J / s Watt is the base unit of Power One watt is equal to 1 joule of work per second
Types of PowerElectrical Power Uses electrical energy to do workMechanical Power Uses mechanical energy to do work (linear, rotary)Fluid Power Uses energy transferred by liquids (hydraulic) and gases (pneumatic)