# Thread: Acceleration, velocity and forces!

1. ## Acceleration, velocity and forces!

Speed humps are to be placed on a street passing a primary school to try and ensure that vehicles do not travel faster than 50km/hr along the street. If a car goes over the humps at more than 25 km/hr then the passengers in the car will receive a nasty jolt. How far apart should the speed humps be placed in order to keep the speed of cars down to safe levels? Million thanks!

2. Originally Posted by BabyMilo
Speed humps are to be placed on a street passing a primary school to try and ensure that vehicles do not travel faster than 50km/hr along the street. If a car goes over the humps at more than 25 km/hr then the passengers in the car will receive a nasty jolt. How far apart should the speed humps be placed in order to keep the speed of cars down to safe levels? Million thanks!
There is insufficient data to give an answer.

3. what info do you need?

4. Originally Posted by BabyMilo
Speed humps are to be placed on a street passing a primary school to try and ensure that vehicles do not travel faster than 50km/hr along the street. If a car goes over the humps at more than 25 km/hr then the passengers in the car will receive a nasty jolt. How far apart should the speed humps be placed in order to keep the speed of cars down to safe levels? Million thanks!
Well, you have an initial velocity (50 km/hr) and a final velocity (25 km/hr) and you want to calculate the distance travelled between the two points A and B where the car has those velocities. So how about you think about what other data is needed to do the calculation and then you tell me ....

5. the acceleration of the car? say it's 3.43209877 m/s^2 and we don't want to excess 25km/h?

6. Originally Posted by mr fantastic
Well, you have an initial velocity (50 km/hr) and a final velocity (25 km/hr) and you want to calculate the distance travelled between the two points A and B where the car has those velocities. So how about you think about what other data is needed to do the calculation and then you tell me ....
The initial and final speeds need to be 25 km/hr as you are travelling between speed bumps.

CB

7. Originally Posted by BabyMilo
the acceleration of the car? say it's 3.43209877 m/s^2 and we don't want to excess 25km/h?
As the maximum acceleration for a car is not the same as the maximum decelleration (with my car I think I can generate more than 1g of decelleration if needed) you also need the decelleration or to state the assumption that these are the same.

CB

8. Originally Posted by CaptainBlack
The initial and final speeds need to be 25 km/hr as you are travelling between speed bumps.

CB
Yes. What's needed is the distance travelled in going from 25 km/hr to 50 km/hr (assuming getting to that speed is posiible, but who knows ....) and then the distance travelled in going from 50 km/hr to 25 km/hr.