Work, Kinetic Energy, Potential Energy & Springs ~ Conservation of Energy

Some definitions:

Energy – The ability to do work

Work – (The force and the displacement have to be in the same direction

Kinetic Energy – This is the energy of motion

Potential Energy – The energy of position

Spring Energy – The energy stored in a spring

Kinetic Energy – the energy of motion

Formula:

Work and Kinetic Energy video

Kinetic Energy – the energy of motion

In 1996, Paul Tracy, while riding in his Indie Car that had a mass of 711 kg, was able to achieve a world record velocity of 413.5 km/h. What was his kinetic energy at that time?

P 290 – Q 2, 3, 4

Potential Energy (gravitational) – the energy of position

Formula:

Potential Energy video2nd Potential Energy video

Potential Energy (gravitational) – the energy of position

Your physics teacher is dangling at the top of one of the McCallum Hill buildings in downtown Regina, at a height of . His mass is . What is his gravitational potential Energy.

Elastic Potential Energy – spring energy

Formula:

Spring Energy video2nd Spring Energy video3rd Spring Energy video

4th Spring Energy video5th Spring Energy video

Elastic Potential Energy – spring energy

A spring with a force constant of is compressed by 12.0 cm. How many joules of energy were required to do this?

Conservation of EnergyThe sum of the initial energies is equal to the sum of the final energies

Formulae:

Initial Final

√ x

x x

x √

x x

A question will dictate which energies are involved. We must consider ALL types of energies in a problem, so that nothing is forgotten. This little table helps to remind you of all the energies as a check-list. The long equation above is greatly simplified in the next step thanks to this table.

Conservation of EnergyA 3.0 kg watermelon is dropped from a building that is 48.0 m tall. Neglecting air-resistance, what is the speed of the watermelon just as it strikes the ground? Does the mass of the melon matter?

Initial Final

x √

√ x

x x

x x

Conservation of EnergyA 2.0 kg block is sliding on a level, frictionless surface when it encounters a spring bumper. The spring has a spring coefficient of 62 N/m and is compressed 4.80 cm. How fast was the block moving?

Initial Final

√ x

x x

x √

x x

Conservation of EnergyPage342.

Questions:29, 32, 36, 52, 54

PowerPower is defined as the rate at which work is done.

The units for power are

http://www.youtube.com/watch?v=9g6hUKx5xVc

Spring Energyhttp://www.youtube.com/watch?v=vmnRZ8IdZKM

100 Discoveries in physicshttps://www.youtube.com/watch?v=Bpid0LBTqWg

Drop Feather and Hammerhttp://www.youtube.com/watch?v=5C5_dOEyAfk

Energy Reviewhttp://www.youtube.com/watch?v=qZ4FFWvZtyo

2nd Potential Energy video