Posts Tagged ‘danger’

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The Terrifying Maths of Running from a Bear … Metric Units

July 17, 2017

METRIC UNITS below. USA UNITS here.

BEAR STATISTICS

Grizzly Bear

Weight:   250kg

Height:   250cm

Top Speed: 56kph  =   16 m/sec

More bear stats here. 

Brown Bear

Weight:  680kg

Height:   250cm

Top Speed: 35kph  = 10m/s

More bear stats here.

Comparing these speeds to the fastest man on earth, Usain Bolt:

Usain Bolt:

Top speed: 243kph =   12m/s

So Usain Bolt could out run a Brown Bear but NOT a Grizzly!

Bears are NOT as dangerous as:

In fact more Americans die choking on their own vomit each year than a re killed by bears.

More death stats here.

But bears are very fast so Park Rangers recommend the following survival tactics:

More bear survival info here.

REF: Dog helps save hikers after grizzly chases them for 20 minutes here.

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1. Stuntman Maths: Car Stunts

August 19, 2014

“With enough stupidity you can get any car to roll over” (MSN AUTO)

What stuntmen and women need is maths!

Maths is essential to the process, from calculating speeds and braking distances to looking at the ratio of the amount of film shot to the length of time of the end sequence. The stunt and crash is outlined, and the co-ordinator explains how he must calculate speeds and stopping distances carefully.

So you want to be a stuntman?

First think of the pain.

Mark Eiden, 52, a professional stuntman (pictured) who is not only afraid of heights, but was once told he likely wouldn’t walk again. Eiden’s had surgery on both arms and shoulders, five knee surgeries, six nasal reconstructions, foot and hand surgery and a facial cast. He fell off the top of a stunt car at 40 mph when the tyre blew. He gaffer taped his ear and continued, despite severe concussion. Northern Express Michigan

1 J Mark Eiden  Northern Express

If you still want to be a stuntman do the Maths:

Rolling a Car:

You can use quick handbrake turn, speed around a corner, fishtail into the curb or some other lunatic thing. The most controlled way to roll a car is to use a ramp.

ramp caranddriver.com

These ramps often have a kicker at the end to add extra lift. Ramp calculations can be complicated, but the simplest way to look at the maths is to determine the angle a car will roll ie. When the Centre of Gravity moves over the base.

Centre of Gravity vs Base Width

The distance between the front wheels in cars is often called the track width.

1a Centre of Gravity

2 Stable Couch3 SUV angleBase vs CofG SUVsTable from Accident Reconstruction Website

4 Bus Centre of Gravity

5 Small car centre of gravity

6 Lambogini Diablo Centre of Grvity

So the Lamobgini Diablo is very hard to roll (build a higher ramp) and it therefore beats the SUV for stability every time.

Balancing on 2 Wheels

A more skilled stunt involves driving a car on two wheels. A very skilled stunt driver can lift the car onto wheels by snaking the car back and forth across the road until it balances on 2 wheels.

From the Centre of Gravity vs Base angles above you can see that the SUV is the easiest car to balance of 2 wheels.

But there is nothing quite as crazy as this SUV stunt:

Saudis changing car tyres, just insane.

Picture 1

View full video here.

Safe Driving Info here

 

 

 

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2. Stuntman Maths: Jumping off a Building

August 19, 2014

The main concern when jumping out off a building is that the airbag (cardboard boxes) cover the drop zone.

The maths calculations involved in jumping off a building are straightforward. You might like to check out How Maths Solved a real murder.

Jump Height that Kills

It doesn’t take much of a fall to cause damage. Sean Hughes, professor of surgery at Imperial College, London. Says “From a height of 3m you could fracture your spine,” he says. “At around 10m, you’re looking at very serious injuries.” (The Guardian, 20 MAY 2014)

Stunt Jump from building from standing start

1 stunt jump from building

As this jump – as in most base jumps – involves a standing start:

2 Mathspig Jump off building

Airbagsupplies.

Stunt jump from building running

We will assume you are no Usain Bolt. His running speed, the fastest in the world, is 44.72 km/h (12.42m/s, 27.44 mph).

We’ll say your running speed on take off is:

Vy = 15 mph = 24.1 kph = 6.7 m/sec

3 Mathspig stuntman running jump

Don’t do this at home.

NB: Airbag dimensions: 20m x 20m x 4 m

Handstand of death

Would you jump off a 25 story building?

 

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4. Build a Creepy Crabmobile

October 3, 2013

Why build a crabmobile?

Crabster CR200

Because working underwater involves huge pressures. To keep it simple the best pressure unit to use is Atmospheres.

 At sea level ( 0 m) the pressure is 1 Atmosphere (atmos).

…………………………………………………………………………….

Every 10 m depth adds 1 atmos pressure.

At 10 m the pressure on your lungs is 2 atmos ie double sea level.

At 20 m the pressure on your lungs is 3 atmos ie triple sea level.

…………………………………………………………………………….

How strong are Your Lungs?

 …………………………………………………………………………….

 You breath air at 1 atmos pressure in and out.

According to The Institute for Structure and Nuclear Astrophysics, Indiana

your lungs only have a capacity:

 …………………………. ± 0.03 Atmos

 …………………………………………………………………………….

hose calc If this comes as a surprise, try it. Try breathing through a hose of, say, 50 cm. 

You will find it quite difficult.

 …………………………………………………………………………….

SCUBA DIVING

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The regulator on the SCUBA tanks feeds you air at a pressure experienced at that depth.

ie. At 10 m you breathe air at 2 atmos pressure

     At 20 m you breathe air at 3 atmos

Pressure at each depth can be calculated using this equation:

 

Pressure formula

 

But here is the Problem:

scuba diver

 …………………………………………………………………………….

AT 30 m ( 100 ft) the disorientation of Nitrogen Narcosis begins.

It’s caused by too much nitrogen dissolving in the blood under pressure.

At 50 m (165 ft) Slowed response. Laughter.

AT 66 m  (217 ft) oxygen toxicity kicks in.

At 70 m (230 ft) Flawed judgment. Hallucinations.

At 90 m stupefaction.

 

pressure chart 2

 

But if you surface too quickly the nitrogen bubbles out in your blood and gives you the bends so called because it is soooo painful.

Ahhhhhh!

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Introducing the Crabster CR 200


crabster_cr200_3

According to Gizmodo, one problem with conventional ROVs – Remotely Controlled Vehicles – is their propellers kick up silt from the sea floor, and their engines struggle in strong currents. But this new underwater explorer sidesteps both of these problems by skittering around the sea floor like a crab.

techno crab

CRABSTER CR 200, developed by a team at the Korean Institute of Ocean Science and Technology (KIOST), can survey shipwrecks and collect data for research. It has 4 pilots. One for the walking and posture. One for the manipulators, cameras and lights. One for the sonar and other scanning equipment. One navigator. This is some creepy crab.

How much pressure can the Crabster withstand?

At 240 m:

p = 0.1 d + 1 = 0.1 x 240 + 1 = 24 + 1 =  25 atmos

Wow! That is  25 times more than sea level.