Question

Can somebody explain why v(horizontal) is negative in the last part of the 3rd question? http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/one-dimensional-kinematics-non-constant-acceleration/MIT8_01SC_quiz05_sols.pdf

Answer 1

It's because the plane came to a stop at "ts". You can see the resolution where it shows \[vhoriz (ts ) - vhoriz (0) = \int\limits_{0}^{ts} ax (t')dt' = ...\]. so if it comes to a stop, then its 0 - \[vhoriz (0) = \int\limits_{0}^{ts} ax(t')dt' = ...\]. becoming - vhoriz(0).

If i'm wrong, please, let me know