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
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