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hrherle
2004-Nov-30, 02:58 AM
I could not think of any better Forum to post my query. The query is quite general and most of us experience it in our general life. :roll:

Consider a bus going on a road. Passenger 'A' is sitting nearer to the front tyres and Passenger 'B' is sitting nearer to the rear tyres. On the way the bus passes through a speed barrier or a hump. Both the passengers experience the effect of the tyres passing over the hump. My question is which of the passengers will experience the greater force and why? :-k

My friends are in the opinion that both the passengers will experience the same force.

frogesque
2004-Nov-30, 03:30 AM
It all depends upon the design of the bus, mass distribution, suspension and where you sit in relation to its dynamic center (I forget the exact terminology for this 'sweet spot')

If you are sitting on the back seat of a bus with a rear section overhanging the rear wheels you definately get quite a kick off a bump, especially if it induces a motion in phase with the bus's natural frequency.

Edit: Your question might be better posted in BABBling and perhaps the BA could move the thread for you.

jaydeehess
2004-Nov-30, 05:11 AM
Make it a symetrical , four wheeled platform and put one passenger above the front tires and one over the rear tires. both will get the same force from going over the spped bump assuming no loss of forward velocity from the front wheels going over the bump.

realistically though if the bus is a rear engine design then there will be a greater ratio of sprung weight to unsprung weight at the rear wheels. This will dampen the change in velocity due to the greater inertia there. A similar situation arises for a front engine design except that in that case it is usually a rear wheel drive which would distribute some weight along the length of the bus in the form of a drive shaft that would not be a factor in a rear engine design.

Sitting above the center of inertia a passenger would feel the least acceleration.

Sitting behind the rear wheels in a front wheel design bus a passenger will feel the greatest accelleration.

Here's another question for you. It is easy to make a rear wheel drive car "fish tail" by applying full throttle while on a wet or icy road What, if any, factors would make it more difficult or easier to do this with a rear wheel bus?

Hint: a flywheel has a large diameter.

Kaptain K
2004-Nov-30, 07:30 AM
Here's another question for you. It is easy to make a rear wheel drive car "fish tail" by applying full throttle while on a wet or icy road What, if any, factors would make it more difficult or easier to do this with a rear wheel bus?
The answer to your question is polar moment of inertia. It is one of the reasons modern race cars are mid-engined. A high polar moment (your rear engined bus) makes it difficult to initiate oversteer (fish-tailing), but hard to catch (correct).

kucharek
2004-Nov-30, 07:40 AM
Make it a symetrical , four wheeled platform and put one passenger above the front tires and one over the rear tires. both will get the same force from going over the spped bump assuming no loss of forward velocity from the front wheels going over the bump.
But the bus may be in some oscillation and how hard you experience the second bump depends on the state of the oscillation when the bump occurs.
The question can't be answered in general, just for a specific design under specific circumstances (e.g. speed).

Harald

Skyfire
2004-Nov-30, 11:04 AM
You wait ages for a Bus question to come along, and then a whole lot of Bus answers come along at once!!! :lol:

kenneth rodman
2004-Dec-01, 07:55 AM
if your question is presupposing that everything else will be the same except where they are sitting then there will be 2 seperate force incidents occuring. when the front wheels hit the bump and when the rear wheels hit the bump.
so the guy in front will feel the front wheel force event first, and the guy in back wil feel the rear wheel force event first