Hence, the total stopping distance = thinking distance + breaking distance = 70 + 245 = 315 feet.
(b) Another car traveling at V mph and its total stopping distance = 125 feet. How fast the car is traveling?
Total distance = thinking distance + breaking distance
=> V feet + V^2 / 20 feet = 120 feet.
=> 20V + V^2 = 2400 (multiply both sides by 20)
=> V^2 + 20 V - 2400 = 0 (subtract 2400 from both sides)
=> The equation is in the form ax^2 + bx + c = 0 where a = 1, b = 20 and c = -2400. The solution to this quadratic equation is given by
(-b + SQRT ( b^2 – 4*a*c ) ) / 2. See
http://en.wikipedia.org/wiki/Quadratic_e…
Substituting the values of a, b and c, yields V = 40 mph.
You can check these answers.
Hope this helps, cutey.
@Hina: I sincerely advise you to read the question(s) carefully before jumping to answering. I increase my marks by average of 20% by doing that.