Question

Two cars collide in a parking lot. Before the collision, their total momentum was 1800 kg m/s to the east. What is their total momentum after the collision.

Answer 1

During collision there is no force on two cars together

So here we can say

$F = \frac{\Delta P}{\Delta t}$

Since force on the system is zero

$0 = \frac{\Delta P}{\Delta t}$

$\Delta P= 0$

$P_i = P_f$

So after collision momentum will remain the same i.e. 1800 kg m/s