1. A speed boat is racing across a lake at 25 meters per second when its motor burns out. It then slowly
comes to a stop over the next 45 seconds. What was its
acceleration?

v = u + a t

where u = initial velocity (25 m/s), v = final velocity (0), a = acceleration, and t = time (45 s). So

0 = 25 m/s + a (45 s)

a = (-25 m/s) / (45 s)

a ≈ -0.56 m/s²

double the distance = divide strength by 4