- #1
Sleve123
- 20
- 0
Homework Statement
A car travels over a humpback bridge of radius of curvature 45m, what is the max speed it can reach before the wheel lose contact with the road?
Homework Equations
mg - R = (mv^2) / r
The Attempt at a Solution
When the car is about to lose contact with the road R tends to zero therefore:
mg = (mv^2) / r
v = (rg)^0.5
v = (450)^0.5 = 21 m/s
The problem I have with this in my head is that this answer seems to only have been resolved when the car is a the peak of the bridge.
For example if the car is somewhere else other than the top, the reaction force would be perpendicular to the tangent, and the component of weight would be opposite this, so:
mgcos(x) - Rcos(x) = (mv^2) / r
where x is the angle between the vertical and the raius at that point,
I just don't understand, could somebody explain.