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sumitmanhas
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Homework Statement
A 870 kg sports car collides into the rear end of a 2500 kg SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 2.9 m before stopping. The police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact.
Part A
What was that speed?
Homework Equations
law of conservation momentum
The Attempt at a Solution
so , we have
mivii + 0 = m1v1f + m2v2f
and since final velocities are same(inelastic collision)
m1v1i = vf( m1 +m2 )
or m1( v1i - vf ) = m2vf - (i)
kinetic enrgy is not conserved
0.5m1v1i2 = 0.5vf2( m1 + m2 )
taking the mivf2 to the left and since 0.5 cancel
m1(v1i2 - vf2) = m2vf2
m1 (v1i + vf)(v1i - vf ) = m2vf2 -(ii)
dividing (i) and (II)
we get, v1 + vf = vf
so from here do i conclude that the final velocities are different otherwise answer makes no sense and instead use subscripts for different final velocities . but final velocity should be same ?
and why is that distance and coefficient of kinetic friction given need help here..