The last equation....
distance= rate/time. You need the average velocity, not the initial. Average here is 1/2 the initial.
The answer given is 173.6m
I solved it this way
60km/h = 16.667m/s
A=V/T 16.667m/s / -.80m/s^2 = 20.834 seconds
D=RT 16.667m/s x 20.834seconds = 347.24m
This is wrong and I do not understand why. Am I doing it right or is the answer wrong?
distance= rate/time. You need the average velocity, not the initial. Average here is 1/2 the initial.
\[v^2 = u^2 + 2as\]
where:
v = final velocity (0 m/s, since the car stops)
u = initial velocity (16.667 m/s, converted from 60 km/hr)
a = acceleration (-8.0 m/s^2)
s = distance
Rearranging the equation to solve for s, we have:
\[s = \frac{{v^2 - u^2}}{{2a}}\]
Plugging in the values:
\[s = \frac{{0^2 - (16.667^2)}}{{2 \times (-8.0)}}\]
Calculating this expression will give you the correct distance required to stop the car.
Let's do the calculations:
\[s = \frac{{0 - (16.667^2)}}{{-16}}\]
\[s = \frac{{0 - 277.77}}{{-16}}\]
\[s \approx 173.6 \ m\]
This confirms that the correct distance required to stop the car is approximately 173.6 meters. Therefore, the answer key is correct and your previous calculation was incorrect.