An ice sled powered by a rocket engine starts from rest on a large frozen lake and accelerates at +15.0 m/s2. At tl = 2.8 s the rocket engine is shut down and the sled moves with constant velocity v. At the 7800 m mark, the sled begins to accelerate at -7 m/s2. What is the final position of the sled when it comes to rest? What is the final position of the sled when it comes to rest?

Question

An ice sled powered by a rocket engine starts from rest on a large frozen lake and accelerates at +15.0 m/s2. At tl = 2.8 s the rocket engine is shut down and the sled moves with constant velocity v. At the 7800 m mark, the sled begins to accelerate at -7 m/s2.  What is the final position of the sled when it comes to rest? What is the final position of the sled when it comes to rest?

Henry · Answer

V1 = a*t = 15 * 2.8 = 42 m/s. d1 = 0.5a*t^2 = 0.5*15*2.8^2 = 58.8 m. V^2 = V1^2 + 2a*d = 0. d = -V1^2/2a = -(42^2)/-7 = 252 m. Final position = 7800 + 252 = 8052 m. mark.