Warm up 11/15Create a KWL as page #9 in your notebook like

below and complete columns K and W

K – what do I already know about converting between kinetic and potential energy (write down at least 5 things about Ke and Pe and converting between the two)

W – what am I confused on about converting between kinetic and potential energy (write down at least two things you do not understand or have questions about)

L – what did I learn about converting between kinetic and potential energy (write down at least 10 facts from the video)

9-3 Conservation of Energy

When two surfaces are touching, the force of friction opposes the motion between the two object◦ Place your hand on the table in front of you and

slide your hand across the table Do you feel any drag keeping your hand from easily

moving? Try it again against the bottom of your shoe Why do you feel more resistance on your shoe than

the desk?

Where’d the energy go?

Energy must be used to overcome friction◦ Think of a roller coaster

The wheels of a roller coaster run along the tracks creating friction between them There is also friction between the cars of the

roller coaster and the air around them The roller coaster can never reach the

same height of the highest hill without help from a chain pulling it up This is because not all of the potential

energy at the top of the hill is converted into kinetic energy Some of this energy is converted into

friction!

How do you get past friction?

A closed system is a group of objects that transfer energy only to each other◦ Ex: a roller coaster, the track and the air around it◦ When a roller coaster runs along its track, some of

the mechanical energy (potential and kinetic energy) is used to overcome friction When this happens, it is turned into thermal energy

which can be felt as heat Think about when you rub your hands together – after a

period of time, your hands feel hot The potential energy at the top of the first hill is

equal to the kinetic energy + thermal energy from friction + sound energy produced

This system is closed

Just like you conserve mass in chemistry, we all also conserve energy in physics◦ The law of conservation of energy tells that

energy is not created or destroyed the total amount of energy in a closed system is

always the same Energy can be converted into other forms, but you will

always have the same amount

Any time energy is converted from one form to another, there is always conversion into thermal energy◦ This is not useful energy

It can not be used to do any additional work

Its all about conservation