Inelastic car collision, answers aren't matching up

AI Thread Summary
In a discussion about an inelastic car collision, a user initially calculated the final velocity incorrectly by adding the momentum of two cars traveling in opposite directions. After realizing the need to subtract the velocities due to their opposing directions, the user corrected the calculation. The correct final velocity of the combined mass post-collision is 3.33 km/h due east. This highlights the importance of considering directional components in momentum problems. The user successfully resolved their confusion with guidance from the forum.
BananasAreCool
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Homework Statement


Car A, having a mass of 1.30 x 10+3kg is traveling at 60.0 km/h due east when it collides with car B, having a mass of mass 1.70 x 10+3kg traveling at 40.0 km/h due west. If the collision is totally inelastic, find the final velocity of car B.
.

Homework Equations


I'm using the equation
m1v⃗ 1+m2v⃗ 2=(m1+m2)v⃗ f​

The Attempt at a Solution


I'm getting 146,000 = (3000)Vf which I'm then dividing to get a velocity of 48.66. But the answer key is telling me 3.33km/h due east. I haven't taken physics in years and am super rusty so any help would be much appreciated.
 
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Hi BananasAreCool, Welcome to Physics Forums.

Did you take into account the fact that the cars are traveling in opposite directions?
 
gneill said:
Hi BananasAreCool, Welcome to Physics Forums.

Did you take into account the fact that the cars are traveling in opposite directions?

That's what I was thinking was the problem, what is the equation for them moving in opposite directions?
 
BananasAreCool said:
That's what I was thinking was the problem, what is the equation for them moving in opposite directions?
I was just able to figure it out, I had to subtract instead of add the two so instead of getting 146,000 I got 10,000, which divided by 3,000 equals to 3.33km/h.
 
BananasAreCool said:
I was just able to figure it out, I had to subtract instead of add the two so instead of getting 146,000 I got 10,000, which divided by 3,000 equals to 3.33km/h.
Yup. Well done.
 

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