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**How can i get an initial speed without acceleration or time?!?!**

## Homework Statement

Hi..heres the problem:

A 4WD travelling East has collided with a stationary car, the 4WD's skid marks are 15m long until the point of collision. The 4WD is sent 35degs South for 15.8m and the car is sent 55degs North for 15m. The car has a mass of 1150kg and the 4WD's is 1600kg. .The coefficient of friction is 0.6.

Find the initial speed of the 4WD before braking in km/h.

this is ALL the info included...

## Homework Equations

s=displacement, mu=0.6, v=final velocity, u=initial velocity, P=momentum, Pi=initial momentum (also just the momentum of 4WD before crash), Pf=final momentum, P'1=momentum of 4WD after collison, P'2=momentum of car after collision, g=gravity(9.8plz), a=acceleration t=time ( numbers after pronumerals signify which vehicle: 4WD=1 , Car=2...dashes between pronumeral and vehicle number mean after the crash eg: P'1)

u= sqr root ( 2mu*g*s)

P=mv

pythagorus= to add the final momentums to get the initial momentum

v^2=u^2 + 2as

s=ut+1/2 at^2 ....(1/2 = half)

v=u+at

## The Attempt at a Solution

to find initial speeds after the crash:

u'1= sqr root:(2*0.6*9.8*15.8)

u'1= 13.63m/s

u'2= sqr root:(2*0.6*9.8*15*)

u'2= 13.28m/2

to find the initial momentum (initial momentum of 4WD)

Pi^2 = (m'1*u'1)^2 + (m'2*u'2)^2

Pi^2=(1600*13.63)^2 + (1150*13.28)^2

Pi= 26623.727 kgm/s

then to find v1= (26623.727)/(1600)

v1= 16.63m/s

from there on i dont know what to do.. I've been advised that the last answer (16.63m/s) was the final speed before the collison...is that right? if so, how can i find the initial speed before braking? im guessing i have to find acceleration, but i dont know how to without time, and visa versa... apparently the initial speed is in the 70's km/h...:S plz help