1 Work and Intro to Energy

OPENER: ( 5 min) 1. Turn to the next available page in your journal 2. Write the date: 3. Write the word ENERGY in LARGE letters across the page, down the page or diagonally. Make it look nice, this is your Energy unit title page. 4. Draw pictures or write words that relate to types of energy, what you use it for, and what you think it is in smaller letters around the title page 5. Take out your energy pretest and complete your energy goal. Turn in.

3 What is work?  In science, the word work has a different meaning than you may be familiar with.  The scientific definition of work:  using a force to move an object a distance (when both the force and the motion of the object are in the same direction.)  SHOW THIS VIDEO:  NEk-14 NEk-14 NEk-14

4 Work or Not?  According to the scientific definition, what is work and what is not? a teacher lecturing to her class a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor a mouse pushing a piece of cheese with its nose across the floor

5 Work or Not?  According to the scientific definition, what is work and what is not? a teacher lecturing to her class a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor a mouse pushing a piece of cheese with its nose across the floor

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7 What’s work?  A scientist delivers a speech to an audience of his peers.  A body builder lifts 350 pounds above his head.  A mother carries her baby from room to room.  A father pushes a baby in a carriage.  A woman carries a 20 kg grocery bag to her car?

8 What’s work?  A scientist delivers a speech to an audience of his peers. No  A body builder lifts 350 pounds above his head. Yes  A mother carries her baby from room to room. No – force exerted upward on baby is not same direction as mother moving baby sideways  A father pushes a baby in a carriage. Yes – father is pushing carriage in the same direction that it is moving  A woman carries a 20 km grocery bag to her car? No - force exerted upward on bag is not same direction as moving bag sideways

9 Formula for work Work = Force x Distance  The unit of force is newtons  The unit of distance is meters  The unit of work is newton-meters  One newton-meter is equal to one joule  So, the unit of work is a joule

10 W=FD Work = Force x Distance Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done?

BUT WAIT! ENERGY IS MEASURED IN JOULES  Work-Energy Principle --The change in the kinetic energy of an object is equal to the net work done on the object. 11