Physics 11 Advanced

Mr. Jean

May 22nd, 2012

The plan:

• Video clip of the day

• Science Fair Questions

• Speed of sound Lab

• Physics of surfing

• E = mc2

• Reflection

• Refraction

Science Fair:

• Who is presenting their science fair project?

Speed of Sound:

• The speed of a sound wave refers to how fast the disturbance is passed from particle to particle; speed refers to the distance in meters which the disturbance travels per unit of time in seconds.

• The speed of a sound wave in air depends upon the properties of the air, namely the temperature and the pressure.

v = 331 m/s + (0.6 m/s/C)•T

• where T is the temperature of the air in degrees Celsius. Using this equation to determine the speed of a sound wave in air at a temperature of 20 degrees Celsius yields the following solution.

Calculations for 20 degrees:

Lab due:

• You have 20 minutes to work on the lab right now!

– When is it due? • May 25th, 2012 @ 3:20pm

– What is due?• Title Page• Observations table• Calculations• Completed questions

Good Surf Days:

• There are two main factors that determine how good the surf will be. – First, there are the conditions that lead to

initial wave formation. These determine the quality and size of the ground swell that will hit the surf spot.

– The second main factor is the local conditions at the surf spot. These have to be right to ensure the swell can create quality waves. Let's look at both of these factors in turn.

Factors which produce waves:

• The three main factors of wave formation– Wind Speed - The greater the wind speed the

larger the wave. – Wind Duration -The longer the wind blows the

larger the wave. – Fetch - The greater the area the wind affects

the larger the wave.

• Closely packed isobars (areas of equal pressure shown on a weather map) mean strong winds. It is these deep low pressures that generate the big swells. The swell will be bigger and last longer...

Making the waves: • How Waves Are Made

– Waves are generated by wind. Offshore storms generate winds which blow on the surface of the sea and create ripples, much in the same way as the ripples in your post surf cuppa are made when you blow on it to cool it down.

• Where it all begins: – Offshore storms generate winds. – The ocean would be almost completely flat without

wind.

• The stronger and longer the wind blows, the more effect it has on these ripples and the larger they become. Initially the waves will just be small chop, but these will soon increase in size.

• As the wind continues to blow and the waves generated remain under the influence of the wind, the smaller waves will increase in size. The wind will get hold of the small waves much more easily than the calm sea surface.

• The wave size is dependent on the wind speed generating it. A certain wind speed will only be able to generate a wave of certain size. Once the largest waves that can be generated for a given wind speed have formed, the seas are "fully formed."

• The longer period waves are faster and move farther ahead of the rest of the slower waves.

• As the waves travel farther away (propagate) from the wind source, they start to organise themselves into swell lines. – Swells are essentially "Wave trains"

When everything is right:

Nova Scotia

• Nova Scotia is quickly becoming a surf destination for surfers around the world. – Especially late August into October for

hurricane season.

Understanding Surfing reports:

• Wave period:

• Total Wave Height:

• Wave Speed:

Big Wave Surfing:

• Video Clip here.

• Here is the biggest I’ve seen in Nova Scotia

Massive Waves: