What is Energy?

• Energy is the ability to do work In other words, energy is transferred by a force moving an object through

a distance (Work = Force x Distance) Ability to cause change Can change itself or its surroundings Measured in Joules (J)

Energy & Work

• Work is the transfer of energyExample: carrying your backpack up the stairs

You do work on the backpack by lifting it against the force of gravity…which requires energy

The energy to do the work comes from your muscles

Muscles receive energy from the food you eat

Energy in food comes from plants that have used energy of sunlight, or animals that have eaten such plants

Kinetic Energy• Energy of motion• Depends on 2 factors: Mass Speed (velocity)

𝐾𝐸=12𝑚𝑣2

What would happen to KE if we doubled the mass? KE would double

What would happen to KE if we doubled the speed? KE would quadruple

Why was KE highest at bottom?

Calculating KE

• A .10 kg bird is flying at a constant speed of 8.0 m/s. What is the bird’s KE?

Potential Energy

• Potential energy is energy that is stored as a result of position or shape

• Has the potential to do work• 2 forms of potential energy Gravitational potential energy Elastic potential energy

Gravitational Potential Energy• GPE depends on height, mass, and gravity

What happens to GPE the higher the object is? increases

𝑃𝐸= h𝑚𝑔m= mass (kg)g= gravity = 9.8 m/s2

h= height (m)

Usually relative to the ground or surface object is usually on

PE depends on where you are considering the reference line to be Has to be relative to

something

Elastic Potential EnergyPotential energy of an object that is stretched or compressed Something is said to be elastic if it springs back to its original shape after it is

stretched or compressed

Forms of energy

Forms of Energy

Mechanical

Thermal

chemical

electricalelectromagnetic

nuclear

Associated with motion and position of objects• Sum of PE and KE• Speeding trains, bouncing balls,

sprinting athletes

Motion of the particles in matter• Faster the particles are moving, more

thermal energy• Slower they’re moving, less thermal

energy

energy stored in chemical bonds

Energy stored in atomic nuclei

Form of energy that travels through space in the form of waves

Energy associated with electric charges

What are some forms of energy you notice around the room?