Potential and Kinetic Energy Explore Activity Page 123

Potential and Kinetic Energy

Explore Activity

Page 123

What is energy?• When an object is able to change it’s

environment, we say the object has energy.• The use of energy involves change• Forms• - radiant, electrical, chemical, thermal

and nuclear• ENERGY = the ability to cause a change

How is all energy divided?

PotentialEnergy

KineticEnergy

All Energy

What is Potential Energy?

oEnergy that is stored and waiting to be used later

oExplain how this flower pot has potential energy.

What is Kinetic Energy?oEnergy in the form of motionoThe greater the mass of a moving

object, the more K.E.oThe greater an objects velocity the more K.E.

WORK

• = The transfer of energy through motion.

• In order for work to take place, a force must be exerted through a distance.

Calculating Work• When a force acts over a distance in the direction of an object’s motion, the work done can be calculated as• work = Force x Distance• W = F x d

Calculating Work

• Which would require more work? Lifting a pack of gum from the floor to waist level or lifting a pile of books through the same distance?

• The amount of work done depends on• Amount of force exerted• Distance over which force is applied

When is Work Being Done?

•Something has to be moving•The motion must be in the same direction as the applied force.

Conservation of EnergyThink about swinging

on a swing.

How does the energy during these

movements change?

Mechanical Energy•The total amount of kinetic and potential energy in a system

Law of Conservation of Energy• Energy may change from one form to

another, but the total amount of energy stays the same.

• The Law of Conservation of Energy states that energy may change form but it cannot be created or destroyed under ordinary conditions.

The Mechanical Energy is not Lost

• Will the swing go back and forth forever?

• Why?

• Where does the energy go?

The Human Body

• What forms of energy are in the human body?

• With your left hand, reach your right shoulder.

• We just converted ________________ energy in our bodies into ________________ energy in our arms.

Balancing Energy Within our Bodies• In our bodies, stored energy (that

found in fat) is lost when work is done or heat is lost by your surroundings.

• To maintain healthy weight, you must have proper balance between energy taken in and energy lost from your body as work or heat.

Food Our Chemical Potential EnergyThink about what you ate this morning. Your body has been chemically changing your food into molecules that can combine with oxygen and be used as fuel.Even if you didn’t eat breakfats, the stored fat in your body is converted to energy.

Measuring Food Energy

• CALORIE• = 4,180 joules• Every gram of fat a person consumes

can supply 9 Calories of energy.• Carbohydrates and proteins supply

about 4 Calories of energy per gram.

Why do our bodies need an energy supply?