“ Work” means many things in different situations.
When we talk about work in physics we are talking about applying a force over a certain distance.
For work to occur a force must produce motion in the direction of the force.
Work = Force x Distance
How fast work gets done is called power
Power is measured in a unit called watts
A powerful machine can do the same amount of work in less time than a less powerful machine
1 watt = 1 joule/sec
Horsepower is the English unit for power.
1 horsepower = 746 watts
Power = work
Energy is defined as the ability to do work
6 Types of energy
Kinetic Energy: associated with motion
Heat: associated with the speed of internal particles
Chemical: bonds atoms together
Electromagnetic: moving electric charges
Nuclear: in the atomic nucleus
Potential Energy: energy of position (energy at rest)
The units of energy are joules
joules are also the same unit as work!
You can think of energy as stored work – that is ready to be released!
Energy cannot be created or destroyed – only changed from one type of energy to another!
Energy with motion
Energy an object has because it’s in motion
All moving objects that have mass have kinetic energy
As mass increases, the KE increases
As speed increases, the KE increases
KE changes more with speed than with mass
KE = mass x speed 2
Kinetic Energy Kinetic energy (joules) KE = ½ m v 2 m - mass of the object in kg v - speed of the object in m/s KE - the kinetic energy in J
Kinetic Energy depends on two things: mass and speed The amount of kinetic energy the cart has is equal to the amount of work you do to get the cart moving A cart at rest has NO Kinetic energy Applying a force can give the cart speed, and therefore kinetic energy. Applying a greater force increases the speed and therefore the kinetic energy Increasing the mass also increases kinetic energy because it takes even more force to push.
Work-Energy Theorem the net work done on an object is equal to its change in kinetic energy