A car weighing 1,600 lb travels around a curve at 70 mi/h. The next car to round this curve weighs 2,500 lb and requires the same force as the first car to keep from skidding.

Question

How fast (in mi/h) is the second car traveling ?

Answer 1

Centripetal force, F_c, is supplied by the friction of the tires and the roadway.

F_c=mv²/r

m = weight/gravity = w/g

F_c=(w/g)v²/r

If the forces are the same to keep from skidding, then:

1600(70)²/(gr) = 1500v²/(gr)

Solving for v

v= √((1600/2500)(70²)) = (4/5)70