- #1
cmcd
- 33
- 0
Homework Statement
A dragstar which weighs 1000kg has a wheelbase 6m long and is assumed to have an unlimited amount of power available to the rear wheels. If the centre of mass of the vehicle is situated 1m forward of and 0.5m above the contact point of the rear wheels and the coefficient of static friction of the tyre/track interface is 0.6 the maximum acceleration which can be developed before the front wheels lift off is...
A- 3.24m/s^2
B - 9.81m/s^2
C- 19.62m/s^2
D- 5.89m/s^2
E- 7.34m/s^2
http://s1372.photobucket.com/user/cmcdona22/media/002_zps0563b57c.jpg.html?sort=3&o=1
http://s1372.photobucket.com/user/cmcdona22/media/003_zps3253eaf5.jpg.html?sort=3&o=0
Homework Equations
F= ma
F_fric= μR
The Attempt at a Solution
Moments about C.o.G. - horizontal distance x vertical force
2R_A x X =2R_B x ( L - X)
2R_A = 2R_B x (L - X)/X
2R_A + 2R_B = mg
2R_B( 1 + (L - X)/X) = mg
2R_B = [X/L] mg
2R_A = [(L - X)/L] mg
Moment about C.o.G. - vertical distance x horizontal force
M_(about A - The rear wheel) = 0 ... for the car not to lift.
vert force x horiz dist
M_A = 2[(X)/L]mg x (L-X) - 2[(X)/L]m ( a - gμ ) x .5
M_A = 0
a_max = 15.886m/s^2
Am I doing the moments wrong?
Or have I gone wrong elsewhere?
Thanks very much,
cmcd