# physics

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.
2 s

(b) Find the distance required for the policeman to overtake the motorist.
3 m

1. drwls

2. Mark

I actually don't know where the 2s and 3m came from, I think it was a typo on my MSWord

3. drwls

(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.

4. Jo

15.97

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