20 POINTS:
Why does the initial hill of a roller coaster need to be steep?

A roller coaster does not have an engine to generate energy. The climb up the first hill is accomplished by a lift or cable that pulls the train up. This builds up a supply of potential energy that will be used to go down the hill as the train is pulled by gravity

Hope this helps! Good luck with future homework and exams!

good for her? ? where is the question?

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s