Inelastic collision: final velocity after collision

Tags:
1. Sep 25, 2016

emily081715

1. The problem statement, all variables and given/known data
You are driving your 1000-kg car at a velocity of(19 m/s )ι^ when a 9.0-g bug splatters on your windshield. Before the collision, the bug was traveling at a velocity of (-1.5 m/s )ι^.
What is the change in velocity of the car due to its encounter with the bug?

2. Relevant equations
pi = pf
m1v1 + m2v2 = (m1 + m2)v

3. The attempt at a solution
i attempted to solve for the change in velocity using the equation outlined below and got answer of -3.0x10^-5. i know this answer is inncorrect but i cannot seem to locate my source of error
Δv=(1.9x10^4)+ (-1.35x10^-2) -19 m/s
1000 +0.009

2. Sep 25, 2016

ehild

Bring the terms of the difference to common denominator, then 1.9x10^4 cancels, and you avoid rounding errors.

3. Sep 25, 2016

emily081715

i am unsure what you mean for me to do/ how to do that

4. Sep 25, 2016

ehild

You calculate the difference $\frac {19\cdot 1000- 1.5\cdot 0.009}{1000+0.009}-19 = \frac{19\cdot 1000- 1.5\cdot 0.009-19(1000+0.009)}{1000+0.009}$
Expand and simplify.

5. Sep 25, 2016

emily081715

i got an answer of -1.8449 x10^-4

6. Sep 25, 2016

ehild

It looks correct, but do not keep more than 3 significant digits.