#### bonfire89

Hi, I'm a Grade 11 physics student who is having a difficult time on this one question.. Any help would be greatly apretiated.

A cyclist is travelling at 21km/h when she sees a stop sign ahead. She applies the brakes and comes to a stop in 15m. The mass of the cyclist and the bike is 73kg.

a)Calculate the acceleration of the cyclist.

b) Determine the coeficient of friction between the road and the bike.

currently for question a I am atempting to use

v1^2 - v2^2 = 2 * d * a

but I am not getting the right answer

Thanks!