Comprehensive Study Notes on Forces and Simple Machines

Definition of a Force:
- A push or pull applied from one object to another.
- Causes a change in motion, direction, or shape.
Ways Forces Cause Change:
- Starting movement
- Stopping movement
- Accelerating (speeding up)
- Decelerating (slowing down)
- Changing direction
- Changing shape
Features of Forces:
- Size (Magnitude)
- Direction
Measurement Unit:
- Forces are measured in Newtons ( $N$ ).

Main Categories:
- Contact Forces: Forces that result from objects touching.
- Examples: Push, Pull, Friction.
- Non-Contact Forces: Forces that exist when objects are not touching.
- Examples: Magnetic, Gravity, Electrostatic.

Balanced Forces:
- Forces that are equal in size ( $\text{magnitude}$ ) but opposite in direction.
- Causes an object to be stationary (not moving) or causes the object to move at a constant speed.
- Example: A central object receiving an applied force of $10\,N$ to the left and an equal force of $10\,N$ to the right.
Unbalanced Forces:
- Forces that are not equal in size, but can act in any direction.
- Causes an object to start moving, stop moving, accelerate, or decelerate.
- Example: An object subjected to a $5\,N$ force to the left and a $20\,N$ force to the right.

Definition of Friction:
- A contact force that slows an object down by acting in the opposite direction to movement.
Useful Applications of Friction:
- Walking / running
- Slowing down moving objects
- Holding objects
Unuseful / Undesirable Friction:
- Ice skating / skiing
- When it produces heat (unless the explicit purpose is heat)
- When moving heavy objects
- When it causes wear + tear
Methods to Reduce Friction:
- Use lubricants (e.g., oil, soapy water, etc.)
- Smooth out / sand a surface, or select a smoother material
- Add wheels to an object

Conventions for Force Diagrams:
- Forces are drawn using arrows.
- The length of the arrow represents the size (magnitude) of the force.
- The arrowhead indicates the direction of the force.
Example Force Diagram:
- Scenario: A ball rolling down a hill (excluding gravity).
- Representation: An object subject to a Push force vector acting to the right and a Friction force vector acting to the left.

Definition of a Simple Machine:
- A machine with little moving parts that is designed to reduce the effort needed to complete tasks.
The Six Types of Simple Machines:
1. Levers
2. Wheel + Axle
3. Pulley
4. Inclined plane
5. Wedge
6. Screw

Component Parts of a Lever:
- Effort: The input force applied to the machine.
- Load: The load or resistance force being moved.
- Fulcrum: The pivot point around which the lever moves.
- Load Arm: The distance between the Load and the Fulcrum.
- Effort Arm: The distance between the Fulcrum and the Effort.
Mechanical Advantage and Arm Length:
- The effort arm must be longer than the load arm to reduce the amount of force needed to move a load.

First-Class Levers:
- Configuration: The Fulcrum is located between the Load and the Effort.
- Functional Characteristics: Provides more force to move an object and increases the distance the object travels.
- Examples: Seesaw, crowbar, scissors.
Second-Class Levers:
- Configuration: The Load is located between the Fulcrum and the Effort.
- Functional Characteristics: Provides a mechanical advantage by providing more force to move an object.
- Examples: Wheelbarrow, nutcracker, bottle opener.
Third-Class Levers:
- Configuration: The Effort is located between the Fulcrum and the Load.
- Functional Characteristics: Increases the speed and distance to move an object.
- Examples: Fishing rod, human arm, shovel.