Potential and Kinetic EnergyPotential and Kinetic Energy

What is Energy???What is Energy???

The ability of an object

To do work

Two Main Types of EnergyTwo Main Types of Energy

PotentialEnergy

KineticEnergy

All Energy

GravitationPotentialEnergy

ElasticPotentialEnergy

ChemicalPotentialEnergy

What is Potential Energy?What is Potential Energy?o Energy that is Energy that is

stored and waiting stored and waiting to be used laterto be used later

What is Gravitational Potential What is Gravitational Potential Energy?Energy?

o Potential energy Potential energy due to an objectdue to an object’’s s positionposition

o P.E. = mass xP.E. = mass x height x gravityheight x gravity

Don’t look down, Rover!

Good boy!

PE

HeightMass

Gravity

ARRGGGG!! NO TRIANGLE

Find the Potential energy of a 20 kg bag of dog food elevated 5 meters above the ground on a shelf.

Mass = 20 kg

Height = 5 m

PE = mx g x h

PE = 20 kg x 9.8 m/s2 x 5 m

PE = 980 J

Find the potential energy of a 65 kg climber on top of Mt. Everest ( 8800 m high).

Mass = 65 kg

Height = 8800 m

PE = mx g x h

PE = 65 kg x 9.8 m/s2 x 8800 m

PE = 5 605 600 J

What is Elastic Potential What is Elastic Potential Energy?Energy?

o Potential energy due compression Potential energy due compression or expansion of an elastic object.or expansion of an elastic object.

Notice the ball compressingand expanding

What is Chemical Potential What is Chemical Potential Energy?Energy?

o Potential energy Potential energy stored within the stored within the chemical bonds chemical bonds of an objectof an object

What is Kinetic Energy?What is Kinetic Energy?o Energy an object has Energy an object has

due to its motiondue to its motiono K.E. = .5(mass x K.E. = .5(mass x

speedspeed22))

Depends on …

Mass

and

Speed

KE = ½ mass x velocity2

KE = ½ M X V2

Mass = 44 kg

Speed = 31 m/s

KE = ½ M x V2

KE = .5 x 44 kg x (31 m/s)2

KE = 21 142 J

What is the kinetic energy of a 44kg cheetah running at 31 m/s?

KE = ½ mass x velocity2

KE = ½ M X V2

Mass = 400 kg

Speed = 5 m/s

KE = ½ M x V2

KE = 400 kg x (5 m/s)2

KE = 5 000 J

What is the kinetic energy of a 400kg elevator descending at a rate of 5 m/s?