Physics: Constant Acceleration3?

Question

Suppose a child driving a go-cart is travelling 4.0m/s when she crosses a line 4.0m from her starting point. She continues, with a steady acceleration of 0.40m/s2 until she crosses a mark 40m from the starting point. How long does it take for her to go from the 4.0-m mark to the 40-m mark?

Please help me.. Thanks! ♥

Answer 1

Ooops! 1 day gone, still no answer! Okay, let me try this out for you.

Forget the starting point and everything. Let's just see the system from the 4m mark upto the 40m mark. What do we have?

initial velocity, u = 4m/s

steady acceleration, a = 0.4m/s^2

distance travelled, s = 40m - 4m = 36m

time, t = ?

The equation is,

s = u*t + (1/2)*a*t^2

at^2 + 2ut -2s = 0

t = [-2*u +-{sqrt(4*u^2-2*a*[-2s])}] / (2*a)

Put the values of u, a and s. You have to take the positive sign for granted in front of the "sqrt" term.

I found the result for you in my notebook. It should be 6.73secons (app.). I hope you have your answer.

Have a nice day.