WORK and Energy

WORK &
Energy

What is work?

● Force times distance

○ In the same direction!

● Joule (J)

○ Metric unit for work & energy
○ J = Nm

Is this work? How Much?

Your backpack weighs 20 newtons. You lift it 1.5 meters off
the floor.

Multiple Choice

Your backpack weighs 20 newtons. You lift it 1.5 meters off the floor.

• 1.5 J

• 20 N

• 30 J

• 50 J

Is this work? How Much?

Your backpack weighs 20 newtons. You carry it for 100
meters.

Multiple Choice

Your backpack weighs 20 newtons. You carry it for 100 meters.

• 2000 J

• Zero Joules!

  (Trick question, F and d are not in the same direction)

• 20 J

• 200 J

Is this work? How Much?

Your backpack weighs 20 newtons. You stand in line for 20
minutes.

Draw

Top of the screen for NO MOVEMENT

Why is the answer Zero Joules?

Bottom of the screen for NOT ENOUGH INFO

Energy

● Energy is the ability to do work
● Measured in Joules (J)

○ Just like work!

● 2 broad categories

○ Kinetic (moving)
○ Potential (stored)

Kinetic energy

● Anything that is moving has KE

○ Mechanical energy
○ Thermal energy
○ Electrical (sometimes)

● KE = 0.5M x V2

○ ½ mass times velocity squared

KE

● 1000 Kg car at 30 m/s

○ 500 Kg x 900 m2/s2 = 450,000 J

● 1000 Kg car at 40 m/s

○ 500 Kg x 1600 m2/s2 = 8,000,000 J

Potential Energy

● Energy due to the nature of the object

○ Stored energy

■ Chemical
■ Nuclear
■ Position (it can fall)
■ Electrical (sometimes)

Dropdown

All of these are examples of Potential Energy​

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