Answer: Trajectory=51m
Displacement=41m
Explanation:
Let's begin by stating clear that movement is the change of position of a body at a certain time. So, during this movement, the body will have a trajectory and a displacement, being both different:
The trajectory is the path followed by the body (is a scalar magnitude).
The displacement is the distance in a straight line between the initial and final position (is a vector magnitude).
According to this, in the description of the object placed at x= -7m on a number line and moving some 12m to the left and then to the right, stopping at x=34m; we are talking about the path followed by the object, hence its trajectory. So, 51 m is its trajectory.
But, if we talk about displacement, we have to draw a straight line between the initial position of the object (x=-7m) to its final position (x=+34m).
Now, being this an unidimensional problem, the displacement vector for this object is 41m.
