Potential and Kinetic Energy Yes, you’re taking notes. You need paper and something to write with.

Let’s review. . . Work occurs when a force moves an object, as long as the force and the object are moving in the same direction.

Energy is defined as the ability to do work so Energy is defined as the ability to do work so. . . if something has energy, it has the ability to do work - energy means that something can be moved with a force - it is the ability to cause change To change the amount of energy an object has, you must do work (apply a force) to the object.

When you draw back on a bow, you do work on the bow When you draw back on a bow, you do work on the bow. - the bow now has energy and can do work on the arrow

When you lift a hammer, you do work on the hammer When you lift a hammer, you do work on the hammer. -the hammer now has energy and can do work on the nail

Law of Conservation of Energy Energy cannot be created or destroyed. Then where does it go??

What do you notice about the total amount of energy? Mechanical energy is broken down into two types: - Potential energy - Kinetic energy What do you notice about the total amount of energy?

Potential Energy – stored energy, energy of position All energy starts out as potential energy. It exists due to an object’s condition or position

Gravitational Potential Energy When position means height, it is called gravitational potential energy. If an object has height, it has potential energy. - The higher an object is, the more potential energy it has.

What do you notice about the potential energy?

PE = mgh potential energy = mass x gravity x height The equation . . . Look familiar? PE = mgh SEE?! Height is important! Wait. . . Is this the same thing as W = Fd?!

Backtrack. . . don’t get lost . . . g = a F = mg W = Fd So. . .all of these are true?! YES!! W = mgd W = mad Fd= mgd mad = mgh Don’t freak out, they all mean the same thing.

Kinetic Energy – energy of motion Things that are moving have energy Kinetic energy occurs when potential energy is converted into kinetic energy Kinetic energy can also be transformed from one object to another

What would affect how much energy a moving object has? Without even knowing the equation, common sense tells you some answers. . . As a truck speeds up, what happens to its kinetic energy? Will you have a lot of kinetic energy carrying a huge packpack?

So, you already know that mass and velocity affect kinetic energy. Here’s the formula: kinetic energy = ½ mass x velocity2 KE = ½ mv2 Note: The fraction and exponent can make the relationships tricky. If you double the velocity of an object, what would happen to the KE? If you double the mass, what happens to the KE? Make sure you know how to isolate each variable!

Now that we know all of that. . . Let’s review conservation. . . .

What type of energy does the ball have at this point?

At the top of the ramp it has 0 velocity so, no KE The energy of the ball is constant during the vertical loop demonstration. At the top of the ramp it has 0 velocity so, no KE It has height so it has PE So the initial energy of the ball is equal to the PE at the top of the ramp At any other point during the demonstration the energy will be equal to the PE at the beginning of the demonstration. The energy at the bottom of the loop is equal to that at the top of the loop but is all converted to KE the ball is moving and has 0 height At the top of the loop the ball has the same energy it had at the top of the ramp. It is made up of PE and KE the ball is moving and has height

What happens between the potential and kinetic energy as the Segway goes off of the cliff?

So. . . can you solve for final velocity? If. . . . . Ei = Ef Then . . . . . PEi + KEi = PEf + Kef So. . . can you solve for final velocity? mghi + ½ mvi2 = mghf + ½ mvf2

2(mghi + ½ mvi2 – mghf) = mvf2 2(ghi + ½ vi2 – ghf) = vf2 vf = 2(ghi + ½ vi2 – ghf)

Sum it up. . . physics - All matter possesses potential energy. - Potential energy becomes kinetic energy and produces motion. Any matter would represent potential energy as long as it is not moving. If it’s moving, kinetic energy is being used. physics