Essence: The motion of a body can be determined by comparing it either to a fixed reference or moving reference point. In this specific experiment, the motion of the body is measured relative to a fixed reference point which contains a sensor. The sensor sends pulses to cardboard reflector which are then used to detect the change in motion of the body. The main aim of this experiment is to establish the graphs of position against time and velocity against time for different motions.
Analysis: The experiment utilized the relationship of position and time to obtain the velocity graph as well as the relationship of the velocity and time to obtain the acceleration graph. From the class notes, the velocity graph is given by the change in position against time. Taking the position to be s and time as t, then the velocity, v, graph is calculated through:
On the other hand, the acceleration, a, graph is obtained by the change in velocity, v, against time, t.
The graphs were expected to resemble given manual graphs but this was not the case. This is because the variation in position and variation in velocity was not constant as well as shaking of the cardboard reflector while walking.
Conclusion: The position against time and velocity against time graphs were obtained from the computerized sensor for all the four tasks. However, the graphs appeared as curved rather than vertical, horizontal and diagonal lines. This was caused by the errors in motion, through irregular motions and errors in reflection, by introduction of echoes caused by shaking the cardboard reflector. The errors can be removed through having the student push a mobile tool such as a trolley containing the reflector, rather than walk holding it.
Expansion: (This lab did not have an expansion part, however, there were questions in all the four parts)
Part 1: In order to produce a V-shaped curve, the motion should be forward to produce a negative line graph then backwards to produce a similar positive line graph.
Part 2: to produce the two differently sloped regions, we increased the motion to get a more inclined slope. To attain a vertical line through moving forward and backward would not be possible since the motion is a variable of time (time cannot be zero). The graph when walking towards a detector has a negative gradient while walking away has a positive gradient. In this lab, the word ‘position’ can be defined as change in space.
Part 3: It does not matter where you stand in a velocity-time graph since the sensor is interested in the velocity only. The two different parts of the graph were produced by increasing the velocity then reducing the velocity. In this lab, the word ‘velocity’ can be defined as change in the velocity of an object.
Part 4: The position-time graph obtained in this part differed from our predictions by being extremely curvy than our prediction. Similarly, the velocity-time graph appeared as a curvy diagonal line compared to our straight line prediction.