3.2 Potential and Kinetic EnergyDate, Section, Pages, etc.

Mr. Richter

Agenda

Warm – Up Review: What is Energy? Notes:

What is Energy Units of Energy Potential Energy Kinetic Energy

Tests Returned

Objectives: We Will Be Able To… Define potential and kinetic energy. Calculate potential and kinetic energy

Warm-Up:

Two objects of equal mass sit on two different window sills. One sits on a second floor window and one sits on a fifth floor window. Which object, if either, has more energy? Why?

On a separate sheet of paper, write your name, then 2-3 sentences explaining your thinking. You have 5 minutes.

Kinetic and Potential Energy

Energy

Review: Energy is a quantity that measures the ability to cause change.

Energy can cause changes in motion: like position, speed, and momentum in physical conditions: like temperature, or turning wood

into ashes and smoke

Energy itself cannot be seen or felt, but we can see evidence of energy in other things. Wind, rolling objects, batteries, gasoline, etc.

Units of Energy

In physics, energy is most commonly measured in Joules [J].

A Joule is a Newton-meter. [J = N-m]

A Joule is a measure of how much energy is required to push with 1 Newton of force for 1 meter.

Another unit of energy less commonly used in physics is the Calorie.

1 Calorie = 4187 Joules

Potential Energy

Potential energy is energy due to position. Objects in unstable positions have stored energy. A stretched spring. A weight on a window sill.

The most common form of potential energy is energy stored due to the height of an object: gravitational potential energy.

Calculating Potential Energy

Gravitational potential energy (Ep) depends on the mass of the object, and its height above the surface below.

What is the gravitational potential energy of a 10-kg object 5 meters above the ground?

4900 J

Kinetic Energy

Kinetic energy is energy due to an object’s motion. Moving objects also have the ability to cause change.

The energy of a moving object is equal to the amount of energy that would be needed to stop the object.

Calculating Kinetic Energy

The kinetic energy of an object depends of the mass of that object and its speed. It is closely related to (but not the same as) momentum.

What is the kinetic energy of a 50-kg skateboarder moving at 3 m/s?

225 J

Wrap-Up: Did we meet our objectives?

Define potential and kinetic energy. Calculate potential and kinetic energy

Homework

p 69 Your Turn a and b Science Fair

Notebook and Research due Wednesday Rough draft of Procedure due Monday 12/3