To calculate the retardation (deceleration) of the train when the brakes are applied, we can use the equation of motion that relates velocity, time, and acceleration. The equation is as follows:
v = u + at
Where: v = final velocity (0 m/s, as the train stops) u = initial velocity (20 m/s) a = acceleration (retardation) t = time taken (10 seconds)
Rearranging the equation to solve for acceleration (a):
a = (v - u) / t
Plugging in the given values:
a = (0 - 20) / 10
a = -20 / 10
a = -2 m/s²
The negative sign indicates that the acceleration is in the opposite direction to the initial velocity. In this case, it represents the deceleration or retardation of the train.
Therefore, the retardation (deceleration) of the train when the brakes are applied is 2 m/s².