Physical Science

Work

Work is a force applied over a distanceIt can also be defined as the transfer of energy

that occurs when a force makes an object movePotential energy is being converted to kinetic

energy when work is being doneIf a force is applied, but no motion results,

scientifically speaking, no work occurs

Work = force X distanceThe SI unit for work is Newtons X meters Newtons X meters is called a Joule, which is

also the SI unit for energy Work is the transfer of energy, so it makes

sense that it is measured in Joules

Power Power is the rate at which work occurs, or

the time it takes to do the work Power = work/ time The SI unit is Joule/seconds, which has a

special name, the watt (W) Watts are small units, so more often we use

kilowatts (kW)

Energy and ChangeEnergy is the ability to cause changeEverything that is moving is changing,

therefore everything in motion must have energy

There are many different types of energyMoney analogy

Types of EnergyKineticPotentialThermalChemical

Kinetic EnergyKinetic energy = energy in the form of

motionDepends on two things:

1. The mass of the moving object2. The velocity of the moving object

The formula for kinetic energy is kinetic energy = ½ mass X velocity2

SI unit for energy is a joule, which is kilograms x (m/s)2

Bill NyeBill Nye Energy

Potential EnergyEnergy doesn’t have to involve motion- it is

just the ability to cause change Potential energy is stored energy, and an

object has potential energy when its position in space gives it the ability to move

Potential energy is converted to kinetic energy when the object’s position in space does change

Types of Potential EnergyElastic Potential Energy = Energy stored by

something which can stretch or compress, such as a rubber band or spring

Chemical Potential Energy = energy stored in bonds between atoms in a chemicalThis is the energy in food or gasoline

Gravitational Potential Energy = energy stored by objects above Earth’s surfaceGPE = mass X acceleration due to gravity X height

What type of potential energies did you observe in the lab?

Formulas So Far – Math ReviewVelocity, Acceleration (2 formulas), Force,

Weight, Momentum, Kinetic Energy, Gravitational Potential Energy

Learn and use your units: they help you remember the formulaEx. Miles per hour- speed/velocity

Miles measure distance Per means division (times means multiplication) Hours measure time= distance divided by time is the formula for speed

and velocityTo show your work:

1) write down the formula, 2) substitute in your numbers/data, 3) write down your solution

Conservation of EnergyThis scientific law states that energy is

neither created or destroyed, meaning that when it is “lost” or “gained,” it is converted from one type of energy to another

Electrical energy is converted to light energy and heat energy in light bulbs- have you ever burned yourself touching a lit light bulb

What else converts electrical energy to thermal (heat) energy?

ConversionsChemical energy in fuel is converted to

kinetic energy and thermal energy in carsChemical energy in food is converted to

kinetic energy and thermal energy in the body

Light energy is converted to chemical energy in the process of photosynthesis in green plants

Light energy is converted to electrical energy in solar panels

Mechanical energyMechanical energy = potential energy +

kinetic energyIt is energy due to the position and motion of

an objectWhen an object has the potential to move, it

has potential energy, and when it fulfills that potential and moves, the potential energy is converted to kinetic energy

Conservation of Energy and FrictionIn the Bill Nye video, the bowling ball does

not return all the way to the point from which he dropped the ball

When pedaling a bike on a flat surface, the bike will not roll forever

This is because friction and air resistance cause some of the energy to be converted to thermal energy rather than kinetic energy

Perpetual Motion MachinesThe idea with perpetual motion machines is

that there is a way to perfectly and completely convert potential energy to kinetic energy and back again, over and overIf there were, we could build perpetual motion

machinesInstead, friction and air resistance always cause

some of the potential energy to be converted to heat energy rather than kinetic energy

Newton's CradlePendulum Waves