fizzics

Finding the distance to a thunderstorm

By mrmackenzie, July 11, 2010 12:50 pm

The thunderstorm this morning reminded me that I was going to post something about calculating the distance to a storm.

Play this video and then replay it, paying close attention to the time index at the bottom. You will need to move your cursor over the video box to keep the time visible.

Lightning from Daniel Dingemanse on Vimeo.

Can you calculate the distance between the flash of lightning and the camera?

Hint: take the speed of sound in air as 340 m/s.

Standard Grade, Telecommunications | distance, speed, speed of sound, time

using frequency to remove vuvuzela noise

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By mrmackenzie, June 30, 2010 9:50 pm

The Physics experts at Sixty Symbols have been playing with a vuvuzela. Here is a film showing their experiments on frequency and sound filtering.

Higher, Intermediate 2, Standard Grade, Telecommunications | filtering, frequency, sound

pressure and high heels

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By mrmackenzie, June 18, 2010 11:07 pm

We deviated from the script a little this week to look at how choice of shoes can affect the pressure put on the ground beneath your feet. If we know the size of the force (F) and the area over which the force is applied (A), then we can calculate pressure using

P=F/A

So when we start talking about shoes, we need to figure out the surface area of the footwear. Luckily, Caitlin had flat-soled shoes on and volunteered to provide data for our calculation. Here is the outline of her shoe, it’s drawn on graph paper so that the area can be calculated quickly by counting the large squares. Each large square is 1 square centimetre – we counted the approximate area by considering only whole squares inside the black outline of the shoe.

shoe outline

Assuming a mass of 50kg, the pressure when wearing the flat shoes is

$P={(50 x 9.8)N}/{(0.0306)m^2}=16000Nm^{-2}$

The red shaded area of our photo shows the reduction in area when heels are worn. With heeled shoes, the area is reduced to approximately 1 square cm per shoe. The change in the pressure is staggering:

$P={(50 x 9.8)N}/{(0.0002)m^2}=2450000Nm^{-2}$

The Science Babe has made a video on this topic. Good physics in here, although I’m not sure she can claim the equation shown above is Newton’s 2nd law. What do you think?

Higher | pressure

is the World Cup hollow?

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By mrmackenzie, June 14, 2010 9:26 am

FIFA claim that the cup is

made of solid 18 carat (75%) gold

but Professor Poliakoff from The Periodic Table of Videos has been looking at data for the trophy and, using the density of gold, he reckons it is hollow.

The wikipedia page the professor mentioned is here.

Interestingly, the professor’s calculator looks almost as old as mine.

Higher | density

Higher webtribe solutions site

Comments (3)

By mrmackenzie, May 25, 2010 10:52 pm

I had a comment that the Higher solutions on the webtribe site were no longer available. I can’t get in to them either but I do have a copy of the site that I use in school when there are filtering issues.

I have uploaded my version of the site to

http://www.mrmackenzie.org/webtribe/ie.html

I hope the person who created the original site does not mind me mirroring the content. Please get in touch is this is a problem and I will remove it. Obviously I am only interested in making this available until Friday.

Higher