Can someone please help me with this? Sally is driving along a straight road for

Question

Can someone please help me with this?
Sally is driving along a straight road for 20 sec. when the lightahead turns red. She immediately applies the brakes whichleads to an acceleration of her car at 5 m/s2 opposed toher forward motion. From this point in time her car comes to a stopin 7.3 sec. Assume she was traveling at a constant speedbefore braking, how far did she travel in those 20sec?

I used s=s0 +v0t +1/2at2    Is this the right equation touse? I came up with 1036m and that seems way to far. Ifthis is not right can you help me out with the right formula touse. If it is right let me know that too please.

Explanation / Answer

First claculate the speed before brake v=u+at, v= final speed = 0 u = initial speed a= -5 m/s2( decelerating) t=7.3s 0= u + (-5)(7.3) u = 36.5m/s so, the speed before braking is 36.5m/s use s=s0 +v0t +1/2 at2 assuming s0= 0 t=20, a=0, ( she was traveling at a constant speed ) v0=36.5m/s the distance travelled = s = v0t s= 36.5 * 20 = 730 m This should be the procedure of doing it. I am not sure if i got all the numbers correct Hope it helps : ) assuming s0= 0 t=20, a=0, ( she was traveling at a constant speed ) v0=36.5m/s the distance travelled = s = v0t s= 36.5 * 20 = 730 m This should be the procedure of doing it. I am not sure if i got all the numbers correct Hope it helps : )

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