Shanghai Tower

As long as acceleration is positive and constant, velocity will increase. When the acceleration becomes zero that does not indicate that elevator has stopped moving but rather it indicates now it is moving with constant velocity. When the acceleration becomes constant and negative it implies that retarding force is applied in the elevator and it's speed will decrease linearly. This complete scenario is best described in Figure (d). Answer = Option (d)

This is just a note about this problem and the other problems relating too the Shanghai Tower that you have posted. It appears as if the pictures you posted are all of the Jin Mao Building, not the Shanghai Tower. Solution: We start off with a positive acceleration and B and D are the only graphs that go up. At the end we have a negative acceleration, so we slow down. The answer is D.

It's completely pointless the graphic A, because it can't reach a negative velocity, so it had to be D

step by step accelaration

For 0 to 3 Sec constant Acceleration, 3 to 6 sec Constant Velocity, and 6 to 9 sec Deceleration. Hence Graph D

It's kind of simple actually. Think of it like this. If there was a hole that went through the earth and out the other side, and a person jumped in without any of the actual things but gravity acting on home like heat, and air resistance, the person would fall and increase his speed until he passed the earth's core. Since he is now on the other side, gravity will now act against him and cause him to slow down to exactly the opposite opening. If he fails to grab the edges then he just continues to repeat the process of technically falling back and forth. Like how Galileo observed a ball roll up and down an inclined plane. After understanding this, it just comes down to whether you know how to read a graph.

Del t(0) al t(3) la aceleración es positiva y constante, luego la velocidad aumenta linealmente. Del t(3) al t(6) la aceleración es cero, luego la velocidad se mantendrá constante. Del t(6) al t(9) la aceleración es negativa y constante, luego la velocidad disminuirá linealmente.

as we know velocity means rate of change per second and rate of change shows that it increases first then it moves at constant after that it moves at decreasing rate

when acceleration is +ve then final velocity is more than that of the initial.and when acceleration is -ve final velocity is less than initial.when accleration is 0, the velocity is uniform