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?

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Distance / Time = Speed so

20m / 40s = 0.5 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?

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Acceleration = Vf – Vi / Change in time so . . .

35m/s – 15m/s / 10 s = 2 m/s/s

2

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 Joulesb. 6.25 Joulesc. 33.3 Joulesd. 75 Joules

Work = force x distance

= 50N x 1.5m

Or = 75 Joules _

Lakiesha, who weighs 550 Newtons, runs to the top of a staircase 5 m tall in 3.5 seconds. How much power is Lakiesha demonstrating?

a. 385 Wattsb. 559 Wattsc. 786 Watts d. 9625 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 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

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?

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B D

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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.

A sound wave is traveling at 343 m/s and has a frequency of 512.5 Hz, what is its wavelength?

a. 0.67 mb. 1.5 mc. 169.5 md. 855.5 m

Speed = frequency x wavelength so

343 m/s = 512.5 Hz x wavelength

Light Spectrum

Visible light is a small part of the electromagnetic spectrum.

Red is the longest wavelength; Violet is the shortest wavelength in visible light.

As wavelength increases, what happens to frequency? Answer: Decreases!

ROY

G

BIV

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.

Ohm’s LawVoltage = Current x Resistance

Standard American Current – 110V @ 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 Amperesb. 15 Amperesc. 3 Amperesd. 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?

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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 poleb. Two north polesc. 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.