Energy and Power COMBINE Energy – Conservation – Power Into 1 summary sheet!

Energy is the ability to CHANGE an object. These types of energy are a result of a CHANGE in……. Work:FORCE Kinetic Energy:VELOCITY Potential Energy: HEIGHT Elastic Energy:SHAPE

Conservation of Energy In a system, the TOTAL MECHANICAL ENERGY never changes Energy can switch forms, but it cannot be created or destroyed. KINETIC POTENTIAL ELASTIC WORK

Examples No matter type of energy transfer, the set up is the same. Even if there is more than one type of energy present TME Initial=TME Final KE + PE + EE + W = KE + PE + EE + W

Energy: Joules (J) Work:W = Fd Kinetic Energy:KE = ½mv 2 Potential Energy: PE = mgh Elastic Energy:EE = ½kx 2

Examples A ball is dropped from a height of 12m, what is the velocity of the ball when it hits the ground? Potential Energy  Kinetic Energy Since all of the energy is transferred, we can set them equal to each other PE = KE m(9.8)(12) = ½(m)v 2  mass cancels m/s = v

Examples A force of 50N pushes horizontally on a 5kg object for a distance of 2m. What is the final velocity of the object? Work  Kinetic Energy Since all of the energy is transferred, we can set them equal to each other Work = KE (50)(2) = ½(5)v m/s = v

Sample Problem A 5kg cart moving at 2 m/s collides with a spring that has a spring constant of k=5N/m. If all of the cars kinetic energy is transferred into elastic energy, what distance will the spring be compressed? Answer: 2m

POWER Power = Energy/ time P = E/t On your equation sheet it lists “Energy” as Work for the top of the fraction. But you can put any type of energy on the top part of this equation.

Sample Problem A 50kg man runs up a 5 meter tall stair case in 10 seconds. How much power does her exert in climbing the stairs? Answer: 245 Watts

Charge Basics and Electrostatic Force COMBINE Charge Basics – Electrostatic Force Into 1 summary sheet!

Electrostatics: Atoms have protons, neutron, and electrons. Only electrons can move! Charge of 1 electron = 1.6E-19 Coulomb (C)

Electrostatics: An object becomes charged when its electrons are shifted or transferred Extra electrons = (-) Fewer electrons = (+)

Sample Problem 1: An object has a charge of -1.76E-18 C charge. How did the object become charged (gain or lose e-) and how many unbalanced electrons does it have? Answer: Gained 11 electrons (Show work and explain why)

Electrostatics: Two charged objects will feel an Electric Force Opposite charges attract (+/-) Same charges repel (+/+) (-/-)

Electrostatics: Calculating the Electric Force k = 9E9 q=charge r= distance between the charges

Sample Problem - 2 Calculating the Electric Force k = 9E9 What is the magnitude of the electrostatic force between two electrons separated by a distance of 1.00 × 10 –8 meter? Answer: x N

Circuits

A circuit provides a COMPLETE path for electrons to move. The flow of electrons is called the current (I). Electrons flow because a voltage (V) provides an energy difference In order to get energy out of a circuit, there has to be resistors (R). Circuits:

Analyze Circuits using an RIVP Table Units  “ R espect I s V ery P owerful” Circuits: RIVP OhmsAmpsVoltsWatts

Series Circuits A circuit in which there is only one current path Circuits:

Series Circuit Current is the same in all resistors I = I 1 = I 2 = I 3 = I 4 Voltage is distributed among the resistors V = V 1 + V 2 + V 3 Total Resistance is the sum of all resistors. R T = R 1 + R 2 + R 3 Circuits:

RIVP TABLE! Sample Problem Series What is the voltage in the 10 ohm resistor?

Parallel Circuits A circuit in which there are several current paths Circuits:

Parallel Circuit Current is the added in all resistors I T = I 1 + I 2 + I 3 Voltage is equal among the resistors V T = V 1 = V 2 = V 3 Total Resistance is the reciprocal of all resistors.3 1/R T = 1/R 1 + 1/R 2 + 1/R 3 Circuits:

RIVP TABLE! Sample Problem Parallel