Question

In the following sketches, ax is the train's acceleration; ti and tf denote, respectively, the time instants when the train starts to slow down and when it stops at the station; xi, (vx)i, xf, and (vx)f are, respectively, the train's position and speed at ti and tf. Which of the following sketches best represents the situation in this problem?

In the following sketches, az is the train's acceleration, tị and tf denote, respectively, the time instants when the train starts to slow down and when it stops at the station, Ii, (UZ), If, and (v)e are, respectively, the train's position and speed at ti and tf. Which of the following sketches best represents the situation in this problem? X;, (0.) 11 xg, (Up to Xp (0) X;, (v) ti X;, (0.) Xp (UX), tf

Answer 1

The situation can be represented as follows:-

Answer! Given that, a train tries to stop. ti = time when train starts to slow down tf a train stopping time .. ni = position of train at ti (Ve), = velocity of train at ti Xf= position of train at tf WxJs = velocity of train at tt So in initial position time is ti, position is xi and velocity is (Vxj. and in final position time is tf. position Xf, and velocity is (vn) f. Also the train comes to rest from motion. so the veloc acceleration of the train i s negative i.e. acts in the opposite direction of motion. The correct representation - is shown in the figure. Here acceleration is Xixi, ti XfVxf, If negative and acts in . the direction opposite to the motion. fig-1 It is not correct because acceleration is along the direction of motion. According to this figure, train will be accelerated. So it is incorrect. fig-2 It is incorrect because the train comes to the final position to the initial position. It is totally incorrect . fig-3 → It is the correct representation as the acceleration is opposite to the direction of motion and comes from initial to final position.