Posts Tagged ‘Math’

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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

Louisa Barama, USA

Louisa Barama, USA

Let’s have a look at this equation:

Figure skate maths1

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 :  vr = 308 RPM

Other spins include:

Mao Asada, Japan, triple Axel

Mao Asada, Japan, triple Axel

Triple Axel spin vr = 220 – 280 RPM

……………………………………………………………………………………………..

 Maximum Triple Axel spin vr = 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 vr = 90 RPM

More info here.

Kim Yuna, South Korea

Kim Yuna, South Korea

…………………………………………….

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 (v1 ) from Angular Velocity (vr ). 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.

Patrick Chan, Canada, Camel Spin

Patrick Chan, Canada, Camel Spin

Patrick Chan, Canada, Triple Axel

Patrick Chan, Canada, Triple Axel

figure skate maths 2

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 vr = 90 RPM

…………………………………………………………………………………

Triple Axel spin vr = 4 x 90 RPM = 360 RPM

That’s about right.

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WINTER OLYMPICS: One Rule Aerial Skiers Cannot Break

February 10, 2018

Aerial 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.

Screen grab from Wired Magazine

Screen grab 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.

trajectory wired magazine

trajectory wired magazine

 

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.

Aerial Parabola final 2

Rocky Maloney Winter X Games Aspen

Rocky Maloney Winter X Games Aspen

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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.

USA UNITS:

Maths of a Car Used as a Weapon

If you are  28  ft away from a car travelling at 35 mph you do not have time to move out of the way.

Some survival tips at the above link.

Stay safe in 2018.

Cheers

Mathspig

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10 Reasons Why Students HATE Maths: BUSTED

December 17, 2017


1. Maths is BORING!: BUSTED

 

2. I’ve got a BAD maths Teacher: BUSTED…………………………………………………………………………….

 3.  Everyone Hates Maths Anyway: BUSTED

…………………………………………………………..

4. Too many different ways to do the………..

same thing: BUSTED

………………………………………………………………………………

5. It’s Too Hard: BUSTED

Come one, a racoon can do it!

 

 

6. You’re either Good at Maths……………………….

or You’re Not: BUSTED

………………………………………………………………….

7. Maths is really SCARY!: BUSTED

………………………………………………………………………….

8. I’ll NEVER use this MATHS: BUSTED

………………………………………………………………..

9. I Hate Answering Questions in…………………

Class: BUSTED……………………………

………………………………………………………………

10. They’re Always Giving Us New Stuff: BUSTED

 

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1. Maths is BORING!

December 9, 2017

Middle School Maths that is AMAZING

psst! That means it’s not boooorrrrinng!

NEW POSTS!

1a. The WORLD POPULATION as ONE BIG CROWD … METRIC

1b. The WORLD POPULATION as ONE BIG CROWD … USA Units

2a. If all the cars in the world were parked together what area would they cover? Metric Units

2b. If all the cars in the world were parked together what area would they cover? USA UNITS

3. If you put the population of the world into AUSTRALIA what area in m2 would we get each?

Meanwhile this Mathspig blog is full of AMAZING middle school maths such as:

KARATE MATHS

HOW MUCH BLOOD CAN YOU LOSE AND SURVIVE?

WHAT VOL OF ALCOHOL IS LETHAL FOR TEENS?

THE TERRIFYING MATH OF RUNNING FROM A BEAR USA UNITS

THE TERRIFYING MATHS OF RUNNING FROM A BEAR METRIC UNITS

PARABOLAS AND THE ART OF SPIITING WATERMELON PIPS

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1b. The WORLD POPULATION as ONE BIG CROWD … USA Units

December 8, 2017

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Why maths is NOT boring!!!!

November 28, 2017

 

Middle School Maths that is AMAZING

psst! That means it’s not boooorrrrinng!

NEW POSTS!

1a. The WORLD POPULATION as ONE BIG CROWD … METRIC

1b. The WORLD POPULATION as ONE BIG CROWD … USA Units

2a. If all the cars in the world were parked together what area would they cover? Metric Units

2b. If all the cars in the world were parked together what area would they cover? USA UNITS

3. If you put the population of the world into AUSTRALIA what area in m2 would we get each?

Meanwhile this Mathspig blog is full of AMAZING middle school maths such as:

KARATE MATHS

HOW MUCH BLOOD CAN YOU LOSE AND SURVIVE?

WHAT VOL OF ALCOHOL IS LETHAL FOR TEENS?

THE TERRIFYING MATH OF RUNNING FROM A BEAR USA UNITS

THE TERRIFYING MATHS OF RUNNING FROM A BEAR METRIC UNITS

PARABOLAS AND THE ART OF SPITING WATERMELON PIPS