A motorcycle starts from a standstill. In 15 seconds it reaches a velocity of 20 m/s. What is the motorcycle's average acceleration?

a = (V-Vo)/t = (20-0)/15 = 1.33 m/s^2.

To find the motorcycle's average acceleration, we need to use the formula for acceleration:

Acceleration (a) = (Change in velocity) / (Change in time)

In this case, the change in velocity is the final velocity minus the initial velocity, and the change in time is the final time minus the initial time.

Given that the motorcycle starts from a standstill (so the initial velocity is 0) and reaches a velocity of 20 m/s in 15 seconds, we can plug these values into the formula:

a = (20 m/s - 0 m/s) / (15 s - 0 s)
a = 20 m/s / 15 s
a = 1.33 m/s²

Therefore, the motorcycle's average acceleration is 1.33 m/s².