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Physics problems

Name: Anonymous 2006-09-19 22:17

Just two physics problems involving kinematics. I have the answers but I don't know how to get to them. Any help would be appreciated.

The problems:

1) An object moving at constant acceleration covers two equal, consecutive, 11 m long segments, the first one in t1 = 0.93s and the second one in t2 = 2.05s . What was the speed of the object (in m/s) at the beginning of the first segment?

Answer: 15.5

2) A terain vehicle, from its intial position, point A should reach a point D which is d= 12.8 km away from the straight road on which the vehicle is on. The point on the road closest to the point D is the point C. The speed of the vehicle while on the road is Vr= 56 km/h while the speed of the vehicle outside of the road is Vt= 34 km/h. Assuming that the vehicle will move along a straight line from point B where it leaves the road, calculate the distance BC so that the overall time ABD is minimum.

Answer: 9.8

I know the the wording is kinda shaky but I just copy pasta'ed it.

Name: Anonymous 2006-09-22 11:25 (sage)

should add the condition that both sides are of equal sign.
Actually, no, I'm wrong. The real mistake is at the end where you neglect that t^2=... has two solutions, and going back to the earlier equations you can see that the negative one is correct. (Whereas with (A-t) it would be the positive one.)

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