In: Physics
A roller coaster reaches the top of the steepest hill with a speed of 6.8 km/h . It then descends the hill, which is at an average angle of 35 ∘ and is 45.0 m long.
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Gravitational acceleration = g = 9.81 m/s2
Mass of the roller coaster = m
Speed of the roller coaster at the top = V1 = 6.8 km/hr = 6.8 x (1000/3600) m/s = 1.889 m/s
Angle of incline the roller coaster descends at = = 35o
Length of the descend = L = 45 m
Height of the descend = H
H = LSin
Normal force on the roller coaster from the incline = N = mgCos
Coefficient of kinetic friction = k = 0.18
Friction force on the roller coaster = f
f = kN
f = kmgCos
Speed of the roller coaster at the bottom = V2
The initial potential and kinetic energy of the roller coaster is equal to the kinetic energy of the roller coaster at the bottom plus the work done against friction.
mgH + mV12/2 = mV22/2 + fL
mgLSin + mV12/2 = mV22/2 + kmgCosL
gLSin + V12/2 = V22/2 + kgLCos
(9.81)(45)Sin(35) + (1.889)2/2 = V22/2 + (0.18)(9.81)(45)Cos(35)
V2 = 19.5 m/s
Speed of the roller coaster at the bottom of the hill = 19.5 m/s