a car moving initially at a speed of 80km/h and weighing 3000 lb is brought to a stop in a distance of 61 m.
a) find the braking force
b) the time required to stop
c) the distance and time required to stop if the car was going 40 km/h
V^2 = Vo^2 + 2a(p-po)
The Attempt at a Solution
this is how I see it, the guy presses his breaks so a force is exerted and so there is an acceleration/deceleration... 0 = 80^2 + 2a(0.061)
a = 80^2 / 2(0.061)
well, I would what to do after getting the acceleration, but this is a huge number.. doesn't seem right.. what have I done wrong? thank you
but also, I'm assuming that 80 km/h is the speed the instant he STARTS BREAKING.. and not his initial velocity for his overall car ride.. this might be wrong.. also, this is assuming that the breaks doesn't spontaneously stop the car?