Is your car safe?By Nick Myers

1. Basics physics of a car crash2. Why do you wear a seatbelt?3. Is a larger car better?4. How safe is your car?

Overview

Will be used throughout the presentation

Kinematic equations

212id v t at

f iv v at

2i fv v

d t

2 2 2f iv v ad

http://www.youtube.com/watch?feature=player_detailpage&v=asJThp-OfpE

Smart fortwo electric

Ford F-150 XLT Super Cab V6

Subaru Outback 2010

Momentum

Physics of a collisionp m v

Subaru Outback 2010

Ford F-150 XLT Super Cab V6

Smart for2 electric

Curb Weight 3,377lbs. 5,167 lbs. 2,094 lbs.

Mass 1,532kg 2,344kg 949kg

MomentumAt 60mph

41,030kgm/s 62,792kgm/s 25,309kgm/s

Speed at 41,030kgm/s

60mph 39.5mph 96.2mph

In the past cars simply got smashed Now they transfer the force around the

cockpit

Little history

From the front end to the cockpit

Crumple Zone

Impulse

What actually hurts you?vF mt

Velocity(mph)

Velocity (m/s)

Average Force over 5m(g’s)

Average Force over 2m(g’s)

Average Force over .66m(g’s)

60 26.8 7.3 18.3 55.5

40 17.9 3.3 8.2 24.8

80 35.8 13.1 32.7 99.1

15 6.7 .5 1.2 3.5

2 2

( )2f i

person person

v vm m a Forc

d

A car hits a building at 17.9m/s or 40mph The 60kg driver will keep moving at 17.9m/s After 0.1 s, he will have traveled 1.8 m

while the car will have traveled only 1.4m

The cars speed at t=0.1s is 9.9m/s

So if he is sitting .4meters away from the steering wheel he hits the steering wheel at 8m/s that’s 18mph!

Not wearing a seatbelt

If after an additional 0.02s he travels with the velocity of the car at 8.3 m/s

he now has a momentum change such that he undergoes a force of 49g’s

That’s not good…

No seatbelt cont.

It depends David Charles Purley, 1977 British grand

prixHit a wall at 108mph and lived!

How many g’s can a person take?

Velocity (m/s)

Velocity(mph)

Average Force over 5m(g’s)

Average Force over 2m(g’s)

Average Force over .66m(g’s)

48.3 108 23.8 59.5 180.3

Before and after

Short answer…. Yes.. Sort of

Are larger cars better?

Inelastic collision

Conservation of Momentum

( ) vB S finalMv mv M m

( )B SMv mvvM m

Now which one do you want?

If both initial velocities are the same then the velocity after collision will be in the direction the large vehicle was going

Small vehicle=high impulse Large vehicle=low impulse

But there is more…

So which vehicle do you want to be in?

Large vehicles tend not to maneuver well They also take longer to stop

Avoiding a crash

Impulse undergone in a collision Stopping distance maneuverability Mass

Making a formula for a safe car

Difficult to measure Slalom speed http://

www.edmunds.com/car-videos/track-tests/2014-chevrolet-corvette-stingray-track-test-video.html

Maneuverability

D=Stopping distance from 60mph (m) F=the Impulse on the 60kg driver in a crash

with a rigid wall at 60mph (N) M=mass of the vehicle (kg) S=Slalom speed (m/s) MSR=Myers Safety Rating Like golf.. Lowest score wins

Introducing the Myers Safety Rating

DF/(M*S2)=MSR

Is your car safe?Car Myers collision scaleSmart Fortwo 2011 2.3933Subaru Outback 2010 0.6820

Ford F-150 XLT SuperCab V6 0.4164

Nissan Titan Pro-4X 2009 0.4645

Chevrolet Malibu Hybrid 0.7012

Honda Civic Si sedan 2010 0.6829Jaguar XKR-S 2012 0.2771

Porsche Cayenne GTS 2009 0.2790

Volkswagon Passat V6 SEL 2012 0.6612Lincoln MKS EcoBoost 0.4858

Winner of original 3: Score of 0.4264Ford F-150 XLT Super Cab V6

Overall Winner! Score of 0.2771Jaguar XKR-S 2012

Wear your seatbelt! Look more in depth when buying a car Vehicle safety comes from the driver

Final Notes

The End

"Edmunds Price Promise®." New Cars, Used Cars, Car Reviews and Pricing. N.p., n.d. Web. 14 Apr. 2014. <http://www.edmunds.com/>.

"Stopping Distance for Auto." Auto Stopping Distance. N.p., n.d. Web. 15 Apr. 2014. <http://hyperphysics.phy-astr.gsu.edu/hbase/crstp.html#c1>.

"Kinematic Equations." Kinematic Equations. N.p., n.d. Web. 15 Apr. 2014. <http://www.physicsclassroom.com/Class/1DKin

"Collision times." Collision times. N.p., n.d. Web. 15 Apr. 2014. <http://footballphysics.utk.edu/pads/collision

"Road & Track's 700ft Slalom." German Car Forum. N.p., n.d. Web. 30 Apr. 2014. <http://www.germancarforum.com/community/threads/road-tracks-700ft-slalom.7451/>.

"Inelastic collision." Wikipedia. Wikimedia Foundation, 18 Apr. 2014. Web. 30 Apr. 2014. <http://en.wikipedia.org/wiki/Inelastic_collision

"Truck Collision." Example. N.p., n.d. Web. 30 Apr. 2014. <http://hyperphysics.phy-astr.gsu.edu/hbase/truckc.html#c3>.

Citations