Archive for the ‘Pythagoras Theorem’ Category


Could you return Andy Murray’s serve?

January 29, 2015


Mathspig is, like, soooooo excited. Tonight I’m gong to watch



Tomas Berdych (CZE) [7] play Andy Murray (GBR) [6] in the Semi-finals at the Australian Tennis Open.

Andy Murray

Andy Murray

Some quick maths.

Tomas Berdych is 1.96 METRES (6 FT. 5 IN.) 

While Andy Murray is 1.91 METRES (6 FT. 3 IN.)

But, but, but …. Andy Murray, who is 26 years old and is 2 years younger than Berdych.

Would you be able to return the serve of a top tennis player?

Here is the serve speed of the of the fastest recorded tennis serves in the world:

1. Top 10 Tennis Serve Speed


How long would it take a tennis ball traveling at these speeds to reach the service line on the other side of the court?

2a Mathspig Tennis Serve 2 maths

BUT … BUT … BUT … 

The tennis ball leaves the servers racket approx 3m above the baseline and travels along the hypotenuse to the service line. We must call in Pythagorus Theorem!!!!

Tennis pythagoras


You can calculate the time it takes a tennis ball to reach the service line for each player in the Top 10 Service Speeds List by using the simple v = x/t equation.

The big question is this:

How fast is YOUR reaction time?

You have to be able to move your racket before the ball arrives.

Can you do it mathspiggies?

You can calculate your reaction time by two methods:

1. The meter rule Method:

3 Drop test 2

4 Reaction Time Chart 2

See details at Top End Sports Website.

2. Online Reaction Time Test

This is the best reaction time clock I’ve seen because it uses a traffic light system. Here is Mathspig’s reaction time:

mathspoig reaction time

Mathspigs reaction time was : 0.33 secs (see above)

So Mathspig would probably be hit on the head by a serve by Samuel Groth.

Could you return Andy Murray’s serve? 

According to Wikipedia fastest service speed times for these two players are:

Andy Murray = 233 km/h (145 mph)

Tomas Berdych = 226.0 km/h (140.4 mph)

Tomas Berdych service speed just beats the fastest female tennis serve by Barbora Záhlavová-Strýcová at 225 km/h (140 mph).

Could Mathspig react in time to return Andy Murray’s server? Could you react in time?

5a Mathspig Andy Murray

Tomas Berdych’s serve would hit the line after 0.29 secs. Once again, I’d still be hit on the head. Ditto the top female tennis players.

Mathspig might lose if she played in the Aussie Tennis Open, but I’m a pig. I’d win serve GRUNT of the match. Ha!


3. Find a Ghost Ship

October 14, 2013

The Ghost Ship, Orlova, disappeared on 4 FEB, 2013 while being towed off the coast of Canada and has not been seen since. The 1,500 tonne 110 passenger Russian vessel is drifting somewhere in the Atlantic Ocean. Missing, Richard Fisher, New Scientist, 5 Oct 2013

Orlova 2

The Lydbov ORLOVA in action. 

Orlova 3

The Lydbov ORLOVA as a Ghost Ship.

Despite 2 separate SOS broadcasts from Orlova life rafts in March,

it has not been found. These SOS signals are the last two ‘sightings’ shown on the map (below),

but an aerial search did not find the GHOST  SHIP.

Map from

Map from

The Problem:

Ghost ships, pirates and illegal fishing vessels do not want to be found. They do not give off radio signals or identify themselves in any way to other vessels. Ghosts ships, in particular, are dangerous because other ships can crash into them at night. Seven ghosts ships have been found since 2000 including an 80m tanker off the coast of Australia. 

GPS is not always accurate. (Scroll down to see error chart: 10. Design Cool Techno Stuff )

Ships must use radar to get instant readings of other vessels in the shipping lane. Can you find a GHOST SHIP Mathspiggies?

bae-radar used by BRitish Fleet



Radar, short for “Radio Detection And Ranging”, sends out short pulse microwave beams that either focus on a narrow area (eg. speed cameras) or scan an entire semi-circular dome (eg War ships). Radar measures the angle and time taken of the reflected echo. This gives the location and altitude (distance and angle) of the airplane or ship.

It is used to detect the location, speed and direction of weather fronts, cars, airplanes, ships and more.

The weather radar beam is typically reaches about 322km or 200 miles. Here is the current radar map produced by the Bureau of Meteorology at the Terry Hills unit north of Sydney (pictured below)


BOM radar 1  sydneyBureau of Met RADAR with protective dome

Bureau of Met RADAR
with protective dome


The Doppler Effect is used to calculate the speed of the ship. Every kid knows the Doppler Effect. eg.  sound of a racing car turning a corner. High pitch approaching, low pitch leaving as sound waves are shorted on approach and lengthened on departure. Today Doppler Radar is automated. This was not possible before computers. eg. World War 2

The Maths:

You are going to do some World War II Radar Operator maths.

To do RADAR MATHS you must THINK HARD and picture what is happening in your mind. All you see on the screen at any one time is YOUR SHIP’S POSITION (in the middle) and a BLIP showing the GHOST SHIP’S POSTION as the microwave beam scans the ocean.

You mark the GHOST SHIP POSITION on screen  and then do these calculations. But remember this …every time you see a blip you have moved too.

Radar Maths 1

 Radar Maths 2

Now we’re going to look at the sort of calculation needed if ships we’re heading on a collision course. You will find all the GHOST SHIP DATA under the RADAR screen (below).

RAdar Maths 3