# Homework Help: Calculating/Simulating Vehicle Braking Force

1. Jun 8, 2007

### Gazzoo

Hi All,

I know this type of question has been asked many times but I need help to clarify for myself if I'm doing the right thing. So here goes...

I am trying to simulate/understand the forces on a vehicle as it is travelling on a road. In particular as it is travelling up hills. So if I have my equations correct the primary negative or braking force would be gravity and would be tangential to the inclined plane. This would be calculated using

F = mg sin(ang)

So for an inclined plane/road at 10 deg, and a 3000kg vehicle the tangential gravitational force would be

F = 3000 x 9.81 x sin(10) = 5110.47 N

So is it correct to assume that this force is applied at the wheel contact surface which may have a radius of say 0.2m producing a torque of

T = F x R = 5110.47 * 0.20 = 1022.09 Nm

So in order to mimic this same force/torque using the car brakes they would need to generate a total negative braking torque of the same amount right?

Do I need to bother with speed/momentum in any manner when trying to calculate this braking force as well as the vehicle is travelling up the incline?

Thanks for your help!

2. Jun 9, 2007

### esalihm

first part is correct, it is mg*sin(ang)

you are talking about a car, a car has tires and tires cause friction
if the car is moving without sliding (I assume this is the case here) you need to consider static friction too, it is static because the contact point of the tire does not move relative to the inclined plane.

the breaks produce a torque that compensates for both of those
and let life stay as simple as it is do not consider any momentum in any of these cases

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