Question

In 1935, a French destroyer, La Terrible, attained of of the fastest speeds for any standard warship. Suppose it took 2.0 minutes at a constant acceleration of 0.19 m/s^2 for the ship to reach its top speed after starting from rest. Calculate the ship's final speed.

Answer 1

The previous answer is terrible. There's no need to complicate things like that.

v_f = v_i + at = 0 + (0.19)(120) = 22.8 m/s

Done

Answer 2

The formula we can use in this problem is:

v^2 = v0^2 + 2ad

d = v0t + 0.5at^2

where v is the final speed, v0 the initial speed = 0, a is the acceleration and d is distance, so:

v^2 = 2ad

d = 0.5at^2

Combining the two equations:

v^2 = 2a (0.5 at^2)

v = sqrt [a^2 t^2]

v = sqrt [(0.19 m/s^2)^2 * (120 s)^2]

v = 22.8 m/s