1. The Energy of Motion
Notes 5.1

2. What is Energy Is the ability to cause change
Many different forms of energy
Chemical
Electrical
Thermal
Nuclear

3. Energy What is Energy? Kinetic Energy: Energy in the form of motion
Running, spinning wheels, etc.
Potential Energy: Stored energy

4. Kinetic Energy The energy in the form of motion
The amount of Kinetic Energy depends on the mass and velocity of the moving object.
More mass = more KE
More Velocity = more KE

5. Potential Energy The stored energy of position.
A flower pot on a window ledge has the potential to fall.
Potential energy depends on position.
A flower pot on the fifth floor has the ability to cause greater change than a flower pot on the first floor.

6. Relationship between PE and KE
Mechanical Energy is the total amount of Kinetic and Potential Energy in a system.

8. Conservation of Energy
Energy can not be created or destroyed, it can only change form.

9. Conservation of Energy
Pendulums

13. How do we transfer energy?
Work is the ability to transfer energy through motion.
The amount of work done can be calculated.
W = F x d

14. Work
Definition: The transfer of energy through motion. A force is exerted over a distance.
Equation: W = F x d

15. Practice Problem:
A dancer lifts a 400N ballerina overhead a distance of 1.4 m. How much work has he done?
W = F x d
W = 400N x 1.4m
W = 560 N  m
W = 560 J

16. Practice Problem:
A game show contestant won a prize by pushing a bowling ball 20m using his nose. The amount of work done was 1470J. How much force did the person exert on the ball?
F = W / d
F = 1470J / 20m
F = 73.5 N

17. Machines

18. What is a Machine? A machine is any device that makes work easier.
Some machines are powered by engines or motors, others are simple and only require one movement.

19. Machines: Making Work Easier by….
Lifting our cars (jacks)
Helping us climb (stairs)
Moving us (wheels and axles)

20. What are Machines?
A device that makes work easier by changing the force.
They change the size of the force needed, the direction of the force or the distance over which a force acts.

21. Advantages of Machines
Can increase the amount of force on an object.
Lug nut
Can increase the distance that the force must work within
Pulley
Can change the direction of the force
Oar

22. Machines
An ideal machine would have the work output equal to the input.
Machines help to overcome obstacles like gravity and friction.

23. Simple Machines There are six types of simple machines Levers Pulleys
Wheel and Axle
Inclined Plane
Screw
Wedge

24. Compound Machine A combination of two or more simple machines
A bicycle

25. Levers
Levers: A rigid bar that moves around a fixed point called a fulcrum.
When you put force into a lever it will produce a different amount of output force.

26. Levers
First Class Lever: The fulcrum is located between the input force and the output force.

27. Levers
Second Class: The output force is located between the input force and fulcrum.

28. Levers
Third Class: The input force is located between the fulcrum and the output force.

29. Simple Machines - Pulley
Pulleys are simple machines made from a rope that fits into the groove of a wheel.
Types of pulleys
Fixed
Movable
Pulley System

30. Simple Machines: Wheel and Axle
A ‘Wheel and Axle’ is a simple machine that consists of two disks (or cylinders), each one with a different radius.

31. Simple Machines: Inclined Plane
An Inclined Plane is a slanted surface that can move an object at a different elevation.

32. Simple Machines: Screw
A Screw is an inclined plane wrapped around a cylinder.
Screws with threads that are closer together have a greater ideal mechanical advantage.

33. Simple Machines: Wedge
A Wedge is a V-shaped object whose sides are two inclined planes sloped towards each other.

34. Power Definition: Power is the rate of doing work. Equation:
To increase power you whether increase the work done in a given time, or do the amount of work in less time.
Equation:
Power = work / time
Remember!!! Work = Force x distance

35. Power Practice Problems:
A figure skater lifts his partner, who weighs 450N, 1.0m in 3.0s. How much power is required?
Power = work / time
Power = (Force x Distance) / time
Power = (450N x 1.0 m) / 3.0 s
Power = 450 J / 3 sec
Power = 150 J/s or…… 150 W (Watts)

36. Watts Watt is the SI unit for power.
It represents the amount of Joules per second
For example, a 40 Watt light bulb requires 40J of energy for every second that it is lit.