9. A roller coaster car starts down a hill from rest. While on the hill, it acce

Question

9. A roller coaster car starts down a hill from rest. While on the hill, it accelerates uniformly. If the trip down the hill takes 6.0 s, and the hill is 45.0 m long, how fast (in m/s) is the roller coaster car going at the bottom of the hill? 10. What is the acceleration (in m/s2) of the roller coaster car in the previous problem? 11. A skydiver jumps out of a stationary helicopter and falls freely for 5 s before opening the 12. Repeat the previous problem if the helicopter moves upward at a constant speed of 5 m/s. parachute. How far below the helicopter (in m) is the skydiver when the parachute opens?

Explanation / Answer

Given,

L = 45 m ; t = 6 s ;

at the bottom,

v = d/t = 45/6 = 7.5 m/s

Hence, v = 7.5 m/s

10)a = v/t

a = 7.5/6 = 1.25 m/s^2

Hence,a = 1.25 m/s^2

11)He willl fall with the acceleration equal to that of gravity

a = g = 9.8 m/s^2

we know from eqn of motion

s = ut + 1/2 at^2

s = 0.5 x 9.81 x 5^2 = 122.63 m

Hence, s = 122.63 m

12)Now he has u = -5 m/s

S = -5 x 5 + 0.5 x 9.81 x 5^2 = 97.63 m

Hence, S = 97.63 m

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