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.

Potential Energy 2 possibilities Gravitational PE - Object lifted to some height Elastic PE - A stretched or compressed object )(springs

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/s 2 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/s 2 h = 100 m 95 kg x 9.8 m/s 2 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

One type of Energy is Electricity Electricity results from electrons moving on a path. Current is the moving electrons the Kinetic Energy Electricity Electricity that is stored is Voltage and that is Potential Electrical Energy The path is called a circuit. There are 2 types of circuits: Series circuits – only one path for the electrons Parallel circuits – more than one path for the electrons.

To figure out which type of circuit.... As the path enters one of the resistances (boxes) you can see there are more lines in and out in a parallel circuit. In the Series circuit, you must go on only one path through each bulb, so if one burns out, the whole string will not light. Series Circuit Parallel Circuit

F. Q G. R H. S J. T 6.Which switches, if opened, will cause the light bulb to stop glowing? It is the only switch in series to both the battery and light.

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

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

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? a. A north and a south pole b. Two north poles c. Two south poles N What is the rule for charges and magnetic poles? LIKE REPELS LIKE! Since the N pole is marked, these must both be south.

Another way energy moves is through waves... Light and sound are two different types of waves. Radiation such as light, heat (infrared radiation) and radioactivity (x-rays and gamma rays) are transverse waves. Sound waves are compression waves. They must have matter through which to travel.

Waves Transverse Waves vibrate 90 o 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 Gamma X rays Ultraviolet Visible Infrared Micro- TV/Radio Radiation Light Light Radiaion waves Waves Shortest to Longest 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? A B D C Highest pitch means short wavelength Lowest volume means smallest amplitude (wave height)

Speed = frequency x wavelength All radiant energy travels at the same speed. 3 x 10 8 meters/sec This is the speed of light through space. Radio waves and nuclear energy waves travel at the same velocity.

A sound wave is traveling at 343 m/s and has a frequency of Hz, what is its wavelength? a m b. 1.5 m c m d m Speed = frequency x wavelength so 343 m/s = Hz x wavelength

Light Spectrum 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. 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.

Quick physics Speed or Velocity = Distance / Time Acceleration = V final – V start / 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....

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? Acceleration = V f – V i / Change in time so... 35m/s – 15m/s / 10 s = 2 m/s/s 5

A young man is standing in line at the grocery store holding a 12-pack of Coke weighing 50 N in his arms which are 1.5 meters off the ground. How much work is he doing? a. 0 Joules b.6.25 Joules c.33.3 Joules d.75 Joules Work = force x distance = 50N x 1.5m Or = 75 Joules _

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

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 1 st Class with the fulcrum in the middle 2 nd Class with the resistance in the middle 3 rd 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.