Question

a cyclist is traveling 15m/s she applies a brake so that she doesn't collide with a wall of 18m away. what retardation must she have?

Answer 1

U=15

V=0

S=18

2as=v^2-u^2

2×a×18 = 0-15^2

36a= -225

a= -225/36

a= -6.25m/s^2

Here the sign is negative so it indicates as a negative acceleration, decceleration or retardation.

(hope that this helps!)