1. Forces Work, Energy, Power
PHYSICS
Forces
Work, Energy, Power

2. Definition
Physics is the study of matter and its motion through space in time
One of the oldest academic disciplines
Physics has close relations with chemistry, math, and biology

3. Forces A force is a push or pull in a particular direction
Forces affect how objects move
They can make objects:
Start moving
Move faster
Move slower
Stop moving
Change direction
Change Shape

4. Forces Measured in Newtons (N) F=ma Usually act in pairs
Kg/m/s2
F=ma
Usually act in pairs
Act in a direction
Forces can usually not be seen, but their effects tend to be more obvious

5. Forces
Balanced
No change in motion
Unbalanced
Change in motion

6. Energy Work Power

7. Work Work is a force acting over a distance to move an object
Force x Distance
Joule (J)

8. Is it work? A teacher applies force to a wall and becomes exhausted
A book falls of a table and free falls to the ground
A waiter carries a tray above his head across a room at constant speed
A rocket accelerates through space

9. What about deceleration?
Negative Work
When a force acts against a moving object to hinder displacement
Displacement?
Example: When a car skids to a stop at a red light, the brakes are exerting a force on the tires to cause them to travel a shorter distance

10. Energy Energy is the ability to do work Power x Time Joule (J)
Potential
Kinetic
Power x Time
Joule (J)

11. Potential Energy Stored energy possessed by an object 2 kinds
Gravitational
Wrecking Ball
Elastic
Bow
Gravitational PE
Mass x g x height

12. Kinetic Energy Energy of motion Many forms KE = ½ x Mass x Velocity2
Vibrational
Rotational
Translational
Energy due to motion from one location to another
KE = ½ x Mass x Velocity2
If velocity increases, KE increases V2

13. Power Power is the rate at which work is done Work / Time
Force x Velocity
Watt = J/s
1 horsepower = 750 Watts

14. Power Let’s talk football Lineman Force is greater with grater mass
Also needs high velocity capabilities

15. What is a Power Rating?
Most machines have a power rating, but where does the rating come from?
Indicates the rate at which a machine can do work to other objects
Power rating on cars describe how fast the car can accelerate
More powerful engines can do an equal amount of work in less time