Answer this...?

Question

A motorboat traveling a straight course slows uniformly from 60km/hr to 40km/hr in a distance of 50m. Whats the boats acceleration?

Answer 1

vf² = vo² + 2aΔx
40² = 60² + 2a(50)
1600 = 3600 + 100a
a = -20 km/h²

Answer 2

One of the more obscure formulas for constant-accleration relations is
delta v = sqrt (2 * a * x ).
First, we decide to get a in m/sec^2. So we convert the beginning and end velocities. to by multiplying by (1000/3600). They are 16.67 and 11.11 m/sec respectively. Substituting,
-5.55 = sqrt ( 2 *a * 50 ) or 5.55^2 = 100*a. Note, a will be negative.
Roughly 5.55^2 is 32. So a is about -0.32 m/sec^2