posted by eric .
A student driver is travelling at 22.2 m/s and sees a school zone ahead. Using her brakes, she accelerates at -2.8 m/s2 to reduce her velocity to 8.2 m/s. How much time did it take to change her velocity?
(deceleration rate)*(time) = (speed change)
She reduces her speed by 14 m/s, so the change is -14 m/s.
time = (-14 m/s)/(-2.8 m/s^2)
= 5 seconds
-14=-2.8t ('-' sign is cancelled from both the sides)
hence time taken is 5 seconds