Quick Physics and Energy Objective 5 Review Quick Physics and Energy

Physics is about Energy and Motion How and why do things move? Do planets move the same way as a ball that is thrown? These are the types of questions physics tries to answer.

Quick physics Speed or Velocity = Distance / Time Acceleration = Vfinal – Vstart / time to change Work (joules) = Force (Newton) x distance (meters) Power (watts) = Work / time

A toy car moves 20 m in 40 seconds. What is the speed of this car? Distance / Time = Speed so 20m / 40s = .5 m/s or . . . . 1 3 2 4 5 6 7 8 9 5 A toy car moves 20 m in 40 seconds. What is the speed of this car?

Acceleration = Vf – Vi / Change in time so . . . 35m/s – 15m/s / 10 s = 2 m/s/s 2 An object is moving at 15 m/s and after 10 seconds the object is moving at 35 m/s. What is the acceleration of the object? 1 3 2 4 5 6 7 8 9

Joe picked up a case of cokes weighing 50 newtons, 1 Joe picked up a case of cokes weighing 50 newtons, 1.5 meters off the floor. The case contained 12 cans. How much work did Joe do? 0 Joules 6.25 Joules 33.3 Joules 75 Joules Work = Force x distance = 50 N x 1.5 m = 75 Joules

Power = Work/time but nothing here is in Joules Work = force x distance so . . . Power = 550N x 5m / 3.5 s = 785.7 watts Alisha weighs 550 Newtons runs to the top of the 5 m tall staircase in 3.5 seconds. How much power is Alisha demonstrating? 385 Watts 559 Watts 786 Watts 9625 Watts

Sir Isaac Newton and the 3 Laws of Motion Considered one of the foremost physicists, Described the motion of all things in a gravity and friction free system. For each of the next slides, write at least 3 examples of each law in action. . .

Newton’s FIRST Law Law of Inertia An object at rest or in motion remains that way until acted upon by an unbalanced force.

Newton’s SECOND Law Force = Mass x Acceleration The greater the force on an object in a single direction the greater the acceleration in that direction will be. If acceleration of a 10 N ball is 20 m/s (sq), what is the acc. of a 5 N ball? A) 5 B) 10 C)20 D) 40

Newton’s THIRD Law Law of Action/Reaction For every action force there is an equal and opposite reaction force. Motion is the result of unbalanced forces on the same object.

There are 6 simple machines Lever 1st Class with the fulcrum in the middle 2nd Class with the resistance in the middle 3rd Class with the effort in the middle To determine the lever classes three, what is in the middle spells FRE. Pulley, Wheel and Axle, Inclined Plane, Wedge and Screw

Mechanical Advantage and Efficiency, Why Not 100% ? Mechanical advantage is how much your force is multiplied by the machine Efficiency is Actual MA/Ideal MA Never 100% due to FRICTION Almost all energy that is not converted into work is converted into heat.

Waves Transverse Waves vibrate 90o from the direction of travel. All electromagnetic waves are in this group. Visible light and the color spectrum are all transverse waves. Water ripple waves and microwaves are also of this type Compression Waves move in the same direction as their vibration. Sound waves, caused by a disturbance, carried through a medium are of this type. Some types of earthquakes are also compression waves.

The Electromagnetic Spectrum Shortest to Longest Gamma X rays Ultraviolet Visible Infrared Micro- TV/Radio Radiation Light Light Radiaion waves Waves Remember: Long – Low – Slow: Long wavelength is a low frequency and slow velocity.

Which of the following waves would have the highest pitch and lowest volume? B D C

Speed = frequency x wavelength All radiant energy travels at the same speed. 3 x 108 meters/sec This is the speed of light through space. Radio waves and nuclear energy waves travel at the same velocity.

Speed = frequency x wavelength so 343 m/s = 512.5 Hz x wavelength A sound wave is traveling at 343 m/s and has a frequency of 512.5 Hz, what is its wavelength? 0.67 m 1.5 m 169.5 m 855.5 m

Light Spectrum Answer: Decreases! Visible light is a small part of the electromagnetic spectrum. Violet is the shortest wavelength, red the longest of visible light. As wavelength increases, frequency __________. Answer: Decreases!

Waves move, so there can be interference . . . When something is an interference, it changes the path of movement. Constructive means it adds to the wave’s energy or amplitude Destructive cancels or decreases the wave’s amplitude

The diagram shows waves approaching a barrier The diagram shows waves approaching a barrier. Which pattern will be formed after the waves pass through the opening in the barrier? After passing through the barrier, it will spread back out and continue on the same path.

Ohm’s Law Voltage = Current x Resistance Standard American Current – 110V @ 15 or 20 Amps Power, measured in Watts is P = VI

Voltage = Current x Resistance 9V = Amperes x 6 ohms or 9V/6ohms = A 9 V battery is connected to a 6 Ohm resistor. How much current will flow through the circuit? 54 Amperes 15 Amperes 3 Amperes 1.5 Amperes

Which of the following electromagnets would be able to pick up the greatest number of paperclips if each one was connected to the same battery? A D C B More current from more wraps means a stronger magnet.

In the diagram above, which poles of the magnets are interacting? What is the rule for charges and magnetic poles? LIKE REPELS LIKE! Since the N pole is marked, these must both be south. N In the diagram above, which poles of the magnets are interacting? A north and a south pole Two north poles Two south poles

Kinetic Energy KE = ½ m v 2 Ex: A moving car has the ability to do work on the light pole if it hits it.

Gravitational Potential Energy or Will it fall? GPE = m g h m is the mass of the object in Kg, g is the acceleration due to gravity which is 9.8 m/s2 on earth and h is the height in meters

Use the formula page! PE = mgh 41 What is the potential energy of the rock? A 59,900 joules B 64,600 joules C 93,100 joules D 121,600 joules m = 95 kg g = 9.8 m/s2 h = 100 m  95 kg x 9.8 m/s2 x 100 =  93,100 joules C

Law of Conservation of Energy Energy can change forms, but is never created nor destroyed Loss in one form = gain in an another form A falling object speeds up as it falls to the ground; PE decreases as KE increases. The KE it has at impact = the PE it had before it fell.

Example: A falling object speeds up as it falls to the ground; PE decreases as KE increases, the KE it has at impact with the ground is equal to the PE it had before it fell

Circuits – 2 types Series circuits are the most simple. One (1) path for the current to travel. Contains an energy source, a path, and a load (something for it to do, like a lamp)

Circuits – 2 types ¢Parallel circuits provide more than one path for the current to travel. ¢Most circuits are parallel, since if one lamp goes out, the others can stay lit. ¢

cause the light bulb to stop glowing? Which switches, if opened, will cause the light bulb to stop glowing? Q R H. S J. T It is the only switch in series to both the battery and light.

USE THE FORMULA SHEET!! ¢What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9 volt electrical source? ¢ A. 0.22 amp ¢ B. 4.5 amps ¢ C. 11.0 amps ¢ D. 18.0 amps V = I R so, 9V = I x 2 ohms or 4.5 amps

Thermal Energy ¢A body contains internal KE due to the motion of its atoms ( they are constantly wiggling and jiggling) ¢Thermal Energy is the total internal KE of a body ¢Temperature is the average KE of a body

Heat- Transfer of Thermal Energy Three forms of heating: 1. Conduction-direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And. . . 

Heat- Transfer of Thermal Energy 1. Conduction-direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And. . .  Three forms of heating:

Heat moves by conduction in solids since the particles are close together and vibrate. . .  ¢43 Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to — ¢A absorb heat by vibrating ¢B transfer heat by fluid motion ¢C emit radiation by reflecting light ¢D exchange heat by direct contact Solids do radiate heat to their surroundings

2 The primary way liquids and gases transmit heat is by the process of — F reflection G conduction H radiation J convection Fluid heat movement is convection. Fluid motion occurs in liquids and gases.