# Speed bump reaction force on a car

1. Jun 29, 2016

### Duffelmop

1. The problem statement, all variables and given/known data
Hi I need to solve the next problem: a car with a total mass of 1950KG hits a speed bump at 19,4m/s. The speed bump is 0,05m high and has a angle of 45°. The car hits the bump with the front axle first. How much force acts on the front axle on the moment of impact.

2. Relevant equations
I started with Newton's law... but I totally messed it up...
Also did some search work, but it made it only more complex for me:
http://www.shimrestackor.com/Code/User_Manual/Sections/Suspension_Velocity/suspension-velocity.htm
3. The attempt at a solution

2. Jun 29, 2016

### haruspex

Are you sure you have quoted the question exactly? Seems like it should be asking for impulse, not force.

3. Jun 29, 2016

### Duffelmop

They asked us to answer how much force was acting on the car in those conditions. It was an exam question this morning, and i really couldn't solve it. It seems for me like there is something missing...

4. Jun 29, 2016

### haruspex

The force is indeterminate, since it will depend on e.g. the rigidity of the tyres. Assume it means impulse.
It's best to work symbolically and only plug numbers in at the end. Let the car be moving initially at speed u, have mass m, and tyres radius r.
Let the impulse from the speed bump be J and the horizontal component of the car's speed immediately afterwards be v.
For simplicity, we can take the car's mass as being m/2 at the middle of the front wheels and m/2 at the middle of the back wheels.
1. In what direction will the impulse be?
2. In what direction will the front tyres be moving immediately after impact, and at what speed? (Assume no bounce.)
3. In what direction will the rear tyres be moving?

Can you write a conservation equation to relate these?