Question 1003210: Can someone please help me with this excercises:
1. A car left skid marks 16 m long when the driver brought it to a quick stop as he was traveling east. Assuming the brakes decelerated the car at -15 m/s^2, how fast was the car traveling when its brakes were first applied?
2. A car is capable of accelerating at a rate of 3.20 m/s^2. If it is going 11.0 m/s when it leaves the curved portion of the entrance ramp to an expressway, how much straightaway does it need to obtain 35.0 m/s before merging with the traffic ?
3. A driver in a car moving at 32 m/s sees a cow sitting on the road 71 m ahead. Can the driver stop in time to avoid hitting the cow if his rate of deceleration is -7.6 m/s^2.
Answer by fractalier(6550)   (Show Source):
You can put this solution on YOUR website! In order to not overload the tutors, you must list these one at a time.
I will do the first one, but relist the others separately.
You can use the formula
Vf^2 - Vo^2 = 2ax
Here your final velocity, Vf = 0, the a = -15, and x = 16.
Plugging in we get
0 - Vo^2 = 2(-15)(16)
-Vo^2 = -480 so that
Vo = 21.9 m/s
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