Aroller coaster starts from rest at its highest point and then descends on its (frictionless) track. its speed is 40 m/s when it reaches ground level. part a what was its speed when its height was half that of its starting point? what was its speed when its height was half that of its starting point? 33 m/s 14 m/s 20 m/s 28 m/s

Given that,

Initial velocity , Vi = 0

Final velocity , Vf = 40 m/s

Acceleration due to gravity , a = 9.81 m/s²

Distance can be calculated as,

2as = Vf² - Vi²

2 * 9.81 *s = 40² - 0²

s = 81.55 m

For half height, that is, s = 40.77m

Vf= ??

2as = Vf² - Vi²

2 * 9.81 * 40.77 = Vf² - 0²

Vf² = 800

Vf = 28.28 m/s

Therefore, speed of roller coaster when height is half of its starting point will be 28 m/s.  

v=ir = 3x15 =45 v