- #1
jaredmt
- 121
- 0
Homework Statement
How great a speed can the car in sample 1.6 (with 2.64 axle ratio) maintain when going up a continuous 10 percent grade (1-ft rise in 10-ft horizontal travel)?
without the incline the top speed is 117 mi/hr, giving the wheel 1513 rpm (calculated in the example)
radius of wheel = 13in
Homework Equations
at 4000rpm (engine speed): engine output = 160hp
W = FV
The Attempt at a Solution
because of the rise, the road gives a normal force of 398 lbs in the horizontal direction
first i converted everything to standard units. then i found the force required to push the vehicle 117mph with 160hp:
F = W/V = 512.9 lb
then added the additional force due to the incline:
F1 = 512.9 + 398 = 910.9 lb
then i solved for the new velocity:
V = W/F1 = (convert) = 65.9 mph
however the answer is supposed to be 72 mph. where was the mistake?