Tuesday, October 18, 2016

Look out a deer!!!

Every Fall students who travel to Colgate for school are usually baffled by two things. First, they are usually surprised about how cold it gets and when it starts snowing. Secondly and arguably more unique to Hamilton, they are startled by the sheer number of deer that roam unabashed by human presence on this campus.  The town of Hamilton itself has created deer management task force to deal with the issue that there were 49 white deer per mi2.  This number per the task force proposal needs to be between 7-10 deer per mi2 to be able to not damage the local ecosystem. So why deer on a physics blog? Due to the increased number of deer, the community deals with more collision with deer than normal.  Also, a deer ran into the SOMAC ambulance the other day, which got me thinking about the energy and momentum changes of a deer on car or vice versa collision.  Let’s do some physics!!

A white-tailed deer weighs on average about 150 lbs. or 68kg and an ambulance weights 2,200 lbs or 997kg. In this situation, the ambulance was at traveling down the road and deer came out of woods and ran right in front of the ambulance and was hit. Let’s say the ambulance was moving at 30mph or 13m/s. For this situation the deer is hit then rolls up the hood and then trapped on the box of the ambulance, making this an inelastic collision where only momentum is conserved. Without any breaking, I calculated the velocities of the ambulance and the deer after the collision.

M(ambulance)V(Ambulance) + m(deer)V(deer) = (M+m)V(deer/ambulance together)
997(13) + 68(0) = 1065 (V)
(V) = 12.17m/s

For this problem, you will notice that for the velocity of the deer I used zero. As the deer, it moving perpendicular to the ambulance, the velocity is not contributing to the change in momentum. The collision alone will decrease the speed of the ambulance by .83m/s. Then if you do the change in momentum of the ambulance and know that the collision occurred over 0.0001s.

1065(12.17)  997(13)= 12,961.05 - 12961=  .05/0.0001  500 N

A good sized force was enacted on the ambulance by the deer. You can also find the deceleration of the ambulance.

500/997kg =  .502m/s2

Overall, it is not a fun experience for either party. Thus, the deer management task force exists.

*This can also be modeled as an elastic collision.
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