## Archive for the ‘algebra’ Category

## QWERTY Math for MAC

April 16, 2018## WINTER OLYMPICS: How ski Jumpers Use Math to Increase their Jump Length

February 16, 2018**While air resistance has little impact on aerial skiers it is a significant factor used by ski jumpers to increase their jump distance.**

**The significant maths for ski jumpers is therefore X-section area.**

**Here is the jump at Pyeong Chang, 2018. Just imagine going down that at top speed!!!**

**Ski jumpers increase their speed going down the ramp by reducing their X-section area:**

**Once they leave the ramp, ski jumpers try to increase their X-section area like Ski Divers to slow their vertical fall. But they have to land safely so they keep their skis at a minimum angle.**

# Here are the X-section areas for Abby Hughes*:

**Here is the formula for Air Resistance of Drag:**

*D *= ½*CApv ^{2}*

**Where C is the drag coefficient or constant, which depends on the shape and spin of an object. It is found by testing the object in a wind tunnel.**

*A* is the X-section Area,

*p* is the density of the air and

*v* the velocity of the object.

**More here.**

**As Abby Hughes has tripled here X-section area in the air she will ****have tripled the vertical drag during her jump. This will slow here decent.**

*Mathspig calculated the X-section area by the old fashioned method of counting squares and rounding off the final count. Mathspig sized the two pics of Abby Huges so that her head was the same size in both pictures.

## Winter Olympics: Why do figure skaters spin so fast?

February 15, 2018

**Here is the sensational pairs team from the 2018 Winter Olympics.**

**But why do ice skaters spin so fast?**

**Here is the math!**

# REASON 1:

Well, mathspiggies, the girl in this video is right. Angular momentum remains constant unless external forces are applied.

# L = mvr

L = angular momentum

v = linear velocity

r = separation of object

Let’s have a look at this equation:

The fastest spin on ice skates was achieved by Natalia Kanounnikova (Russia) with a maximum rotational velocity of 308 RPM (rotations per minute) at Rockefeller Centre Ice Rink, New York, USA on 27 March 2006. See Guinness Book of Records.

## Record spin : v_{r} = 308 RPM

Other spins include:

## Triple Axel spin v_{r} = 220 – 280 RPM

……………………………………………………………………………………………..

## Maximum Triple Axel spin v_{r} = 402 RPM

Skaters can spin faster during a triple axel jump because there is no friction from the ice slowing their spin.

To complete a quad axel, it’s estimated that the skater would have to rotate in the air at:

## 540 rpm.

…………………………………………………………………………………

## Camel spin v_{r} = 90 RPM

More info here.

## …………………………………………….

# REASON 2:

## How can a figure skater move from

## a camel spin into a very fast standing spin?

Now, mathspiggies, you must separate Linear Velocity (v_{1} ) from Angular Velocity (v_{r} ). Linear Velocity is measured in m/sec ie. it is the speed of, say, a skaters foot around the circle. Angular Velocity is measured in either RPM (Revolutions Per Minute) or degrees or Radians per minute. Ie. It is the rate of spin. We can’t judge how many m/sec a skaters foot is moving in a circle. We can only see how fast they spin. In other words, we see their Angular Velocity. When a skaters foot is in the Camel position that foot travels in a very big circle.

But when that same foot is in a Triple Axel postion it moves in a very, very small circle.

By halving the radius, firstly, a skater’s Linear Velocity doubles due to the conservation of angular momentum.

Then, secondly, by halving the radius the circumference of the circle moved by , say, the skaters foot is halved.

Overall, by doubling the velocity around the circle and halving the circumference a skater increases their rotational velocity by a factor of 4.

Look at the numbers:

## Camel spin v_{r} = 90 RPM

…………………………………………………………………………………

## Triple Axel spin v_{r} = 4 x 90 RPM = 360 RPM

That’s about right.

## WINTER OLYMPICS: One Rule Aerial Skiers Cannot Break

February 10, 2018Aerial skiers aim for height rather than length. Their aerial flight times are much smaller than ski jumpers so air resistance has minimal impact.

In fact, there is one law the aerial skiers cannot break. It is the law of gravity.

Here is an equation for projectile motion from Wired magazine.

The equation for projectile motion also applies to **Motorbike Jumps** and **Longbow Arrows**.

Here is the x-y graph for different launch angles.

You can go to this page for complete calculations. Aerial skiers twist and turn but their CENTRE OF GRAVITY must follow this graph. More on centre of Gravity at The Great Back Pack Attack ie.

The centre of gravity of Aerial Skiers must follow a

# parabolic curve.

## Hello 2018 This is why you need maths!

December 30, 2017**Hello Little Munchins,**

**,…………………………………………..****…………………………….**

**Maths can save your life. How? Read on.**

**,…………………………………………..****…………………………….**

**Sadly, a car has been used as a weapon again in my city, Melbourne. **

**,…………………………………………..****…………………………….**

**When talking to science types about the Maths of a Car Used as a Weapon they say ‘Yeah! Right! As if you are going to stand around doing the maths when a car is heading towards you!!!!.’****……………………**

# NO!**…………………………………………..****……..**

#### You don’t do the maths in a crisis. You do it before hand. And it will change your view of car safety for all time.

# METRIC:

**Maths of a Car Used as a Weapon **

#### If you are 9 m away from a car travelling at 60 kph, you DO NOT have time to move out of the way.

**Some survival tips at the above link.**