If a car experiences a force of 2000 N over a time of 0.2 sec, what is the impulse?

Students design a model roller-coaster track. they place a rubber ball at the highest point on the track and let it go. the ball rolls along the track pulled only by the force of gravity. eventually, it comes to a stop. which change to the design will result in the ball moving the greatest distance?

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.

What does the law of conservation of mass state?