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
u=22.2m/s
a=-2.8m/s2
v=8.2m/s
t=?
v=u+at (equation)
8.2=22.2+(-2.8)t
8.2-22.2=-2.8t
-14=-2.8t ('-' sign is cancelled from both the sides)
14/2.8=t
5=t
hence time taken is 5 seconds
To find the time it took for the student driver to change her velocity, we can use the equation of motion:
v = u + at
where:
v = final velocity = 8.2 m/s
u = initial velocity = 22.2 m/s
a = acceleration = -2.8 m/s^2
t = time
We can rearrange the equation to solve for time (t):
t = (v - u) / a
Substituting the given values:
t = (8.2 - 22.2) / -2.8
t = (-14) / -2.8
t = 5 seconds
Therefore, it took the student driver 5 seconds to change her velocity.