Lab Set #2 Notes and Ideas

ENERGY WORK AND POWER

Work W = Force * Distance F is always in the direction of motion and parallel. A Force can be exerted on an object, while no work is done.

Energy Kinetic = 1/2mv 2 Potential due to gravity = mgh Elastic = 1/2kx 2 (also Known as Hooke’s law) W net = Change in Kinetic Energy W G = -Change in Potential Energy

Example A 1000kg Coaster moves from point 1 to 4. A) What is the gravitational potential energy at 2 and 3 relative to 1? B) What is the work done by gravity from start to finish?

Forces Conservative Force – Work done does not depend on path taken, but rather the initial and final positions. (Gravity) Nonconservative force – Depends on the path taken (Friction)

Equations To Know Work Energy Principle W NC = ΔKE + ΔPE Conservation of Mechanical Energy\ Conservative Forces only KE 2 + PE 2 = KE 1 + PE 1

Energy Energy Cannot be Created or Destroyed simply transformed. When its seems we lose energy in a problem that is called a dissipative force and that is usually found in the form of Friction or Air resistance

POWER Average Power = Work/ Time Watt is the unit of power (1 Watt = 1Joule/s) Horsepower = 550 ft*lbs/ s = 746 W Average Power = W/t  F*d/t  Force * Average Velocity = P Efficiency  e = P out / P in

Momentum and Collisions

p = mv Net Force = ma  Δp/Δt Momentum

Impulse = F Δt Elastic Collisions (bounce off each other) Kinetic energies are the same before and after the collisions. So Energy and momentum are conserved. Inelastic Collisions (stick together) – kinetic energy is not conserved, it is transferred to a different form. Collisions and Impulse

Momentum Before = Momentum After Elastic Collision - M a V a + M b V b = M a V a + M b V b Inelastic Collision - M a V a + M b V b = (M a + M b )V ab Conservation of Momentum

Momentum is still conserved, but is conserved in each direction. P a x + P b x = P’ a x + P’ b x P a y + P b y = P’ a y + P’ b y Collisions in 2 dimensions

Optics

Rough surfaces

Imaginary Image

Convex Mirror F = r/2

Concave Mirror

Ray Diagrams Step 1 – Principal Ray

Ray Diagrams Step 2 – Central Ray

Ray Diagrams Step 3 – Focal Ray

Mirror Equation

Magnification

Index of Refraction

Snell’s Law Angle of incidence Angle of refraction

Power of Lens

Lensmaker’s Equation

Simple Harmonic Motion

SHM In mechanics and physics, simple harmonic motion is a type of periodic motion where the restoring force is directly proportional to the displacement and acts in the direction opposite to that of displacement.

Hooke’s Law F = -kΔx

Circuits

Electric Current

Ground Definition – common conductor to which real circuits are connected to provide continuity in the circuit.

Ohm’s Law Resistance – a measure of the degree to which conductor opposes an electric current through it Voltage = Current x Resistance  V=IR Unit = Ω = Ohm’s = 1V/A

Electric Power

Series Circuit

Parallel Circuit

Kirchhoff’s Rules Rule 1 – Rule of Junction – at any junction the amount of current in = the amount of current out. Rule 2 – Loop Rule – The sum of changes in potential around any closed path of a circuit must be ZERO.

How to solve using Kirchhoff 1. Label the currents and their directions 2. Identify the unknowns 3. Use the Junction rule 4. Use the Loop Rule 5. Solve the equations for unkown.