HONORS PHYSICS
Introduction
Matter & Energy
Math Review
Kinematics
Defining Motion
Graphing Motion
Kinematic Equations
Free Fall
Projectile Motion
Relative Velocity
Dynamics
Newton's 1st Law
Free Body Diagrams
Newton's 2nd Law
Static Equilibrium
Newton's 3rd Law
Friction
Ramps and Inclines
Atwood Machines
Momentum
Impulse & Momentum
Conservation Laws
Types of Collisions
Center of Mass
UCM & Gravity
Uniform Circular Motion
Gravity
Kepler's Laws
Rotational Motion
Rotational Kinematics
Torque
Angular Momentum
Rotational KE
Work, Energy & Power
Work
Hooke's Law
Power
Energy
Conservation of Energy
Fluid Mechanics
Density
Pressure
Buoyancy
Pascal's Principle
Fluid Continuity
Bernoulli's Principle
Thermal Physics
Temperature
Thermal Expansion
Heat
Phase Changes
Ideal Gas Law
Thermodynamics
Electrostatics
Electric Charges
Coulomb's Law
Electric Fields
Potential Difference
Capacitors
Current Electricity
Electric Current
Resistance
Ohm's Law
Circuits
Electric Meters
Circuit Analysis
Magnetism
Magnetic Fields
The Compass
Electromagnetism
Microelectronics
Silicon
P-N Junctions
Transistors
Digital Logic
Processing
Integration
Waves & Sound
Wave Characteristics
Wave Equation
Sound
Interference
Doppler Effect
Optics
Reflection
Refraction
Diffraction
EM Spectrum
Modern Physics
Wave-Particle Duality
Models of the Atom
M-E Equivalence
The Standard Model
Relativity
DYNAMICS
Newton's 1st Law
Free Body Diagrams
Newton's 2nd Law
Static Equilibrium
Newton's 3rd Law
Friction
Ramps and Inclines
Atwood Machines
Silly Beagle
Newtons's 3rd Law of Motion
Newton’s 3rd Law of Motion, commonly referred to as the Law of Action and Reaction, describes the phenomena by which all forces come in pairs. If Object 1 exerts a force on Object 2, then Object 2 must exert a force back on Object 1. Moreover, the force of Object 1 on Object 2 is equal in magnitude, or size, but opposite in direction to the force of Object 2 on Object 1. Written mathematically:
Newton's 3rd Law Equation
This has many implications, some of which aren’t immediately obvious. For example, if you punch the wall with your fist with a force of 100N, the wall imparts a force back on your fist of 100N (which is why it hurts!). Or try this. Push on the corner of your desk with your palm for a few seconds. Now look at your palm... see the indentation? That’s because the corner of the desk pushed back on your palm.
running tiger
Although this law surrounds your actions everyday, often times you may not even realize its effects. To run forward, a cat pushes with its legs backward on the ground, and the ground pushes the cat forward. How do you swim? If you want to swim forwards, which way do you push on the water? Backwards, that’s right. As you push backwards on the water, the reactionary force, the water pushing you, propels you forward. How do you jump up in the air? You push down on the ground, and it’s the reactionary force of the ground pushing on you that accelerates you skyward!
As you can see, then, forces always come in pairs. These pairs are known as action-reaction pairs. What are the action-reaction force pairs for a girl kicking a soccer ball? The girl’s foot applies a force on the ball, and the ball applies an equal and opposite force on the girl’s foot.
How does a rocket ship maneuver in space? The rocket propels hot expanding gas particles outward, so the gas particles in return push the rocket forward. Newton’s 3rd Law even applies to gravity. The Earth exerts a gravitational force on you (downward). You, therefore, must apply a gravitational force upward on the Earth!
