Forces Work, Energy, Power PHYSICS Forces Work, Energy, Power

Definition Physics is the study of matter and its motion through space in time One of the oldest academic disciplines Physics has close relations with chemistry, math, and biology

Forces A force is a push or pull in a particular direction Forces affect how objects move They can make objects: Start moving Move faster Move slower Stop moving Change direction Change Shape

Forces Measured in Newtons (N) F=ma Usually act in pairs Kg/m/s2 F=ma Usually act in pairs Act in a direction Forces can usually not be seen, but their effects tend to be more obvious

Forces Balanced No change in motion Unbalanced Change in motion

Energy Work Power

Work Work is a force acting over a distance to move an object Force x Distance Joule (J)

Is it work? A teacher applies force to a wall and becomes exhausted A book falls of a table and free falls to the ground A waiter carries a tray above his head across a room at constant speed A rocket accelerates through space

What about deceleration? Negative Work When a force acts against a moving object to hinder displacement Displacement? Example: When a car skids to a stop at a red light, the brakes are exerting a force on the tires to cause them to travel a shorter distance

Energy Energy is the ability to do work Power x Time Joule (J) Potential Kinetic Power x Time Joule (J)

Potential Energy Stored energy possessed by an object 2 kinds Gravitational Wrecking Ball Elastic Bow Gravitational PE Mass x g x height

Kinetic Energy Energy of motion Many forms KE = ½ x Mass x Velocity2 Vibrational Rotational Translational Energy due to motion from one location to another KE = ½ x Mass x Velocity2 If velocity increases, KE increases V2

Power Power is the rate at which work is done Work / Time Force x Velocity Watt = J/s 1 horsepower = 750 Watts

Power Let’s talk football Lineman Force is greater with grater mass Also needs high velocity capabilities

What is a Power Rating? Most machines have a power rating, but where does the rating come from? Indicates the rate at which a machine can do work to other objects Power rating on cars describe how fast the car can accelerate More powerful engines can do an equal amount of work in less time