BELLWORK 9/8/15

What are your goals for after graduation?

**Give me 4 sentences minimum**

FIND YOUR NEW SEATS AND BE IN THEM, PLEASE!

Chapter 15.1

Energy

Learning Objectives Section 15.1

Describe the relationship between work and energy

Relate kinetic energy to the mass and speed and calculate these quantities

Analyze how potential energy is related to an object’s position and give examples of gravitational and elastic potential energy.

Solve Equation that relate an object’s gravitational potential energy to its mass and height.

Give examples of major forms of energy and explain how each is produced.

Energy and its formsIn an avalanche, a mass of loose snow, soil, or rock suddenly gives way and slides down the side of a mountain.The avalanche releases a great amount of energy.

How are work and energy related? Energy is the ability to do work

Work is the transfer of energy

Work and energy are closely related. • Energy is known by the changes it causes. • Work is done when a force moves an object through

a distance. Energy is transferred by a force moving an object through a distance.

• Both work and energy are typically measured in joules (J).

Energy has different forms

A. The sun gives off energy in the form of heat and light.

B. Plants convert sunlight into food. C. People convert food energy into muscle movement.

What is Kinetic Energy?

Energy of Motion.

What is Kinetic Energy?

What factors does Kinetic Energy depend on?

Mass Speed

Kinetic Energy

Doubling the mass in the formula doubles the kinetic energy.

Doubling the speed quadruples the kinetic energy.

Formula:

Who has more kinetic Energy? Who has the least?

Which has the most KE? 80 km/hr truck

Which has the least KE? 50 km/hr motorcycle

80 km/hr 50 km/hr

80 km/hr

Practice Problems Kinetic Energy

A 0.10 kilogram bird is flying at a constant speed of 8.0 m/s. What is the bird’s kinetic energy?

What is Potential Energy?

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

Gravitational Potential Energy

Energy stored in position

So what does gravitational potential energy depend upon? (PEg)

Mass HeightAcceleration due to gravity- The potential energy increases when an object is raised to a higher level

Gravitational Potential Energy PEg

The unit for mass is kilograms.

The unit for height is meters.

Acceleration due to gravity, g, has a value in SI units of 9.8 m/s2 on Earth.

The unit for gravitational potential energy is joules.

Formula:

More on Potential Energy

Height is measured from the ground or floor or some other reference level.

Doubling either the mass of the object or its height doubles its gravitational potential energy.

Examples of Gravitational Potential Energy

This diver has gravitational potential energy as she stands at the end of a diving board.

She gained the potential energy by doing work—by climbing up the steps to the diving board.

Practice Problems - PEg

What is the potential energy relative to the water surface of a diver at the top of a 10.0 – meter high diving platform. Suppose she has a mass of 50.0 kilograms.

Elastic Potential Energy

The potential energy of an object that is stretched or compressed is known as elastic potential energy.

Something that is elastic springs back to its original shape after it is stretched or compressed.

Major Forms Energy

ENERGY

motion of electric charges

bonding of atoms

motion of objects

internal motion of particles

changes in the nucleus

The ability to cause

change.MECHANICA

L

ELECTRICALCHEMICAL

NUCLEAR

THERMAL

joules (J)

ELECTROMAGNETIC

Energy in fields

Mechanical Energy

The energy associated with the motion and position of everyday objects is mechanical energy.

Mechanical energy is the sum of an object’s potential energy and kinetic energy.

Thermal Energy

The total potential and kinetic energy of all the microscopic particles in an object make up its thermal energy.

When an object’s atoms move faster, its thermal energy increases, and the object becomes warmer.

Increasing the temperature – increases the thermal energy

Molten metals contains great deal of thermal energy

Chemical Energy

Chemical energy is the energy stored in chemical bonds.

When bonds are broken or formed; the released energy can do work. All chemical compounds, including fuels such as coal and gasoline, store energy.

Burning wood – is a combustion reaction which breaks bonds thus producing thermal energy

Electrical Energy

Electrical energy is the energy associated with electric charges.

Electric charges can exert forces that do work.

Electromagnetic Energy

Electromagnetic energy is a form of energy that travels through space in the form of waves. Visible light and X-rays are examples of electromagnetic energy. A. Lightning bolts transfer electric charge.B. Galaxies are giant structures in space that typically contain billions

of stars. The stars give off enormous amounts of electromagnetic energy.

Nuclear Energy

The nucleus of an atom is held together by strong and weak nuclear forces, which can store an enormous amount of potential energy.

• The energy stored in atomic nuclei is known as nuclear energy.

• Nuclear fission releases energy by splitting nuclei apart.

• Nuclear fusion releases energy when less massive nuclei combine to form a more massive nucleus.