consider the motion of roller coaster in upward direction
v₀ = initial velocity as it starts travelling vertically upward = 45 rad/s
v = final velocity when it becomes stationary for a moment = 0 m/s
a = acceleration of roller coaster in upward direction = - 10 m/s²
t = time passed before the roller coaster becomes stationary
using the kinematics equation
v = v₀ + at
inserting the values
0 = 45 + (- 10) t
0 - 45 = (- 10) t
t = - 45/(- 10)
t = 4.5 sec
