Answer:
![v_2=9.89 m/s](https://img.qammunity.org/2020/formulas/physics/high-school/br7ftem24qsnma0bjjnuralfy6bhp1rb4p.png)
Step-by-step explanation:
Given
mass of roller coaster (m)=500 kg
Height of high hill=9 m
height of low hill=4 m
As total Energy is conserve therefore
Total Energy at high hill=Total Energy at low hill
Energy =Potential Energy + kinetic Energy
![mgh_1+(mv^2)/(2)=mgh_2+(mv_2^2)/(2)](https://img.qammunity.org/2020/formulas/physics/high-school/xfl2c7x80ejum40en6yw84yotwh1xoczil.png)
At top Kinetic energy is zero
![g* 9+0=g* 4+(v_2^2)/(2)](https://img.qammunity.org/2020/formulas/physics/high-school/we682yolw49hvxz40ch8i5kthx0ttv3jlr.png)
![2* 5* g=v_2^2](https://img.qammunity.org/2020/formulas/physics/high-school/jw9t5yafmbrexgiscnt6ey2pgf26hqupcr.png)
![v_2=√(2* 5* 9.8)](https://img.qammunity.org/2020/formulas/physics/high-school/ooqm9w5o1mbvuq2xdc0bf4zc775jd4otnd.png)
![v_2=9.89 m/s](https://img.qammunity.org/2020/formulas/physics/high-school/br7ftem24qsnma0bjjnuralfy6bhp1rb4p.png)