# Calculate Impact Force Of a Truck Hitting a Deer

Trying to calculate the impact of an 8000 lb. truck moving at a rate of 55mph, hitting a 200 lb deer that is standing still in the middle of the road. Does assuming it is a localized hit make any difference? What i mean is, if the deer was hit from the back, and his 200lb wieght was focused in a 2 foot wide area on the front of the truck. Thanks!

## Answers and Replies

Homework Helper
What a cruel question :D

Perhaps it would be best to idealize and use conservation of momentum.

The reason i am trying to figure it out is for an insurance claim. Not trying to be cruel and evil lol.

sophiecentaur
Gold Member
2020 Award
The change in momentum is easy to calculate: The speed after impact would have been
55X(8000/8200) mph, assuming the deer sticks to the front of the vehicle. This is probably not too relevant as the brakes would have been applied before - or immediately after the impact.

But the Force involved is less easy. The same change in momentum can be achieved by a range of forces and the times they are applied. It's called Impulse.
Impulse = Force X time
Small force X long time can be the same as large force X short time
I assume you didn't have a timer or video camera running so you can't estimate the time taken for the actual impact. I guess your insurer will be aware that any force estimate you were to give would be very speculative. Perhaps they are waiting for you to make a preposterous claim which they can then reject? Are they, perhaps, implying that you were driving too fast?

There is a lot of data, taken from human collisions, which connects front-end damage to vehices (and humans) by body impact with speed of vehicle. You could, perhaps, conduct your own experiments - using insurance inspectors as your subjects.

They are insuring me for the body damage on the truck, but there is also damage to my front axle. They are trying to say there is no way that a hitting a deer could crack a weld on the axle, thats why i'm trying to figure out impact forces to prove them wrong(not looking for exact numbers even). I am pretty sure hitting a 200 lb object in the road, me going 50mph or so, is enough impact to do the damage. BTW, i'll be honest, i'm not that good at complicated math, so any help would be greatly appreciated.

sophiecentaur