- #1

rhader

- 4

- 0

I have a problem I am working on and was wondering if someone could point me in the right direction.

The problem:

I need to calculate a force to apply to a given area of the front of a vehicle in relaticely small collision / impact with both a stationary and possibly a small moving object the size roughly of a softball for volume.

The scenario:

A car is driving at any given speed and a rock is either a) stationary and hits the front bumper or under neath of the car. or b) is propelled from a car in front and accelerates backwards at a given speed and impacts the vehicle.

I basicallly need to calculate the force that object will have at the impact point.

assumptions:

vehicle speed = 80km/hr, 50miles / hr

vehicle weight = 3000lbs, 1360 kgs

object size (small rock size of a softball)

circumference of a regulation softball = 12" / 0.3048

Now given that the radius would be:

C = 2 pi * r

r = C / ( 2 *pi )

r = (0.3048 m) / (2 * pi)

r = (0.3048 m) / (6.28318)

r = 0.0485 m

Volume of the softball-sized rock

V = (4/3) * pi* (r^3)

V = (4/3) * pi * (0.0485 m)^3

V = (4/3) * pi* (1.142E-4 m^3)

V = 4.782E-4 m^3

Find the mass of the rock using density

m = (2,750 kg / m^3) * (4.782E-4 m^3)

m = 1.315 kg

Now two given scenarios:

1) the rock is not moving and the car is traveling at 50mph. What the impact firce of the rock be?

- here there would obviously be a few factors at play. a) impact upwards b) force of car pushing down c) side angle forces

- for simplicity sake let's assume the rock hits something underneath the car and there is an equal distribution of forces updward and downward acting here and no acceleration of the vehicle at the point of the impact over a given time...

2) second scenario the rock is moving towards the car we can assume at a speed of 50mph also.

Any thoughts on simplifying the above problem?

much appreciated!