Mechanical Energy

Monuments Review

So you can commit it to M.E.M.Re

Lets start with work What is work?

The transfer of energy by mechanical means; is done when a constant force is exerted on an object in the direction of motion.

Work 2 What does that mean?

My version: Work is the energy we use/get on/from an object moving because a force (push pull) was applied.

I move an object I am doing work.

Picture time Draw a picture:

Work 3 What is the equation for work?

W = Fd (cos Θ)

What does that cos mean?

We can have positive, negative, and 0 work.

Work 4 Positive: When the force and the direction

are pointed in the same direction

Negative: When the force and the direction are pointed in opposite directions

Zero: When the force and the direction are perpendicular.

Work video http://youtu.be/_N0r1ignq1w

Kinetic energy What is Kinetic energy?

Kinetic means ‘to move’ so it is energy from motion.

Picture time Draw a picture:

Equation What is the equation for KE?

KE= ½ mv2

Don’t forget the squared velocity!

KE video http://youtu.be/2MkAZu6QW0I

Potential energy What is potential energy?

It is energy stored, in this class we are dealing with potential energy gravitation. So the stored energy is based on how high up is the object.

Picture time Draw a picture:

Equation What is the equation for PE?

PE = mgh

PE video http://youtu.be/pNl8flwGWD8

Mechanical energy What is Mechanical energy?

Energy of an object due to its motion or position.

ME 2 What does that mean?

Mechanical energy is if a physical object is moving or can move.

Picture time Draw a picture:

Equation What is the equation for Mechanical energy.

MEi=MEf

What I start with is what I will end with.

Concept question A man rides an elevator to the 3rd floor of

his building. (12 m high), his identical twin takes the stairs. If the stairs go around the entire building who has more Energy when they reach the room?

Boxy (5kg of mass) falls from 2m up, how fast is boxy

moving just before he hits the ground?

You try. A roller coaster cart (100kg) is traveling at

40m/s at the bottom of the track. How high will the cart climb up the track?

Pendulum A mass of 3kg is held 0.5m above the

ground. If released from rest how much Kinetic energy will the mass have at the bottom of the swing?

Pendulum 2 How much KE will it have at 0.25m above

the ground?

Hill A man on top of a hill 7m tall slides down to

the bottom. If the man has a mass of 90kg and we ignore friction how fast is the man traveling ½ way down the hill?

Hill 2 What is the KE of the man at the bottom of

the hill.