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**[SOLVED] [attempt?] car accident problem.**

**1. Homework Statement**

http://hypertextbook.com/physics/mechanics/momentum-two-three/accident-reconstruction-1.pdf [Broken]

**2. Homework Equations**

Pix=Pfx

Piy=Pfy

v^2 = v0^2 + 2 ax

Fk=MkN

W=mg

F=ma

**3. The Attempt at a Solution**

01.

Fk = MkN

100 N = Mk (130 N)

0.769 = Mk

car tires = 0.769 --- but then, i'm not sure of the units.

0.769 (0.7) = 0.538

truck tires = 0.538 --- again with the units.

02.

W = 13600 N

W = mg

13600 = m (9.8 m/s^2)

1387.755 kg = m

Fk = MkN

Fk = 0.769 (13600 N)

Fk = 10458.4

F = ma

10458.4 = 1387.755 a

7.536 m/s^2 = a

v^2 = v0^2 + 2 ax

0 = v0x^2 + 2 (-7.536) (8.2)

123.59 = v0x^2

11.117 m/s = speed of car

W = 69700 N

W = mg

W = 7112.245

Fk = MkN

Fk= 0.538 (69.700)

Fk = 37498.6

F = ma

37498.6 = 7112.245 a

a = -5.272 m/s^2

v^2 = v0^2 + 2 ax

0 = v0^2 + 2 (-5.272) (11)

115.984 m/s = v0^2

10.769 m/s = speed of truck

03.

Pfx=Pix --- i know i wrote the other way earlier, but i'm copying my weird notes.

(1387.755) (11.117) cos (33) + (7112.245) (10.769) cos (7) = 7112.245 v

88958.823 = 7112.245 v

v of truck = 12.508 m/s

(1387.755) (11.117) sin (33) + (7112.245) (10.769) sin (7) = 1387.755 v

17736.701 = 1387.755 v

v of car = 12.781 m/s

I asked my teacher and he said he vaguely remembering that the velocities were supposed to be 11?, but he and I couldn't find fault with the set up. I tried recalculating, and I came up with the same answer, which frustrates me a bit.

04.

As for number four, I read the facts given repeated times, but I'm still at a loss for how to approach it. I realize that I'm supposed to use parts 01.-03. though.

Thanks.

**:**D

Sorry, it's a bit long.

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