posted by Mark
A motorist travels at a constant speed of 34.0 m/s through a school zone; exceeding the posted speed limit. A policeman, waits 7.0 s before giving chase at an acceleration of 3.9 m/s2.
(a) Find the time required to catch the car, from the instant the car passes the policeman.
(b) Find the distance required for the policeman to overtake the motorist.
Are 2s and 3 m your answers? Please show your work
I actually don't know where the 2s and 3m came from, I think it was a typo on my MSWord
(a) Measure time t from the instant the policeman passes the cop.
The speeder's distance travelled is
X1 = 34 t meters
The policeman's distance travelled (for t>7) is
X2 = (1/2)*3.9 (t-7)^2
Set X1=X2 and solve for t.
That is when the speeder is caught.