we're looking for the change in the cars momentum . the formula to identify the cars momentum is Δp=m*vf-m*vi . In this case m= mass , vf= velocity final, and vi= velocity initial . The mass is how much the car weighs , which is 4 kg . Velocity final would be 8 m/s since that's how fast it last was . Velocity initial would be 3 m/s since it had first started at that speed . Now we can jus plug it into the formula .
