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# [PHYSICS] Determining Vehicle Speed Immediately Prior to Collision

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Data:

Net Force of Collision: 20,000 pounds/90,000 Newtons

Mass of Vehicle: 6,500 pounds/29,250 Newtons

Time Duration of Collision: 0.15 seconds

Vehicle Speed after Collision: 0

Other Data:

Car applied brakes around 24 meters before the steel swing gate.

Coefficient of Static Friction: around 0.732

Coefficient of Kinetic Friction: around 0.798

I do realize this is a physics problem, but I can't seem to figure out the math behind it. Anybody willing to help?

physics
Dec 9, 2015

#1
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You don't say what you are trying to calculate, so I've assumed you want to find the approaching velocities.

Also you can't have a mass in Newtons, so I've converted your 6500 pounds (mass) to kg.  (there is a difference between lbf (force) and lb (mass)). On second thoughts I should probably have assumed kinetic friction.  However, static friction is usually higher than kinetic friction, so perhaps I've used the right numerical value after all!

Dec 9, 2015
edited by Alan  Dec 9, 2015

#1
+15

You don't say what you are trying to calculate, so I've assumed you want to find the approaching velocities.

Also you can't have a mass in Newtons, so I've converted your 6500 pounds (mass) to kg.  (there is a difference between lbf (force) and lb (mass)). On second thoughts I should probably have assumed kinetic friction.  However, static friction is usually higher than kinetic friction, so perhaps I've used the right numerical value after all!

Alan Dec 9, 2015
edited by Alan  Dec 9, 2015