Toy Car Movement Effect of Different Weights Casey Wu Shanghai American School Pudong High School September, 2009

Transcription

1 The Question Toy Car Movement Effect of Different Weights Casey Wu Shanghai American School Pudong High School September, 2009 How will different weights added to the toy car affect its movements? The Plan Independent Variable: weight Three values chosen for investigation: 0g, 100g, 200g Controlled variable: toy car As shown below in Figure 1, I will let my car run with no added weights for the first segment of the experiment. On the second trial, I will add a weight of 100 grams to the toy car. For my last variable, I will run my car with an added weight of 200 grams. Expectations I expect my car to travel slower when greater weights are added to it. Marking the Videos Figure 1 My toy car with 0g added weight. Origin set at the left end of meter stick. Figure 2 My car with 100g of added weight. Origin set at the left end of the meter stick. For each video, I marked a point for every third frame, so it is easy to see the acceleration of the toy car. Figure 3 My car with 200g of added weight. Origin set at the left end of meter stick.

2 Data Tables Here is the raw data for three trials after copying from Logger Pro into Excel. Table 1 Data for my toy car with 0g added weight. Table 3 Data for my toy car with 200g added weight Table 2 Data for my toy car with 100g added weight From the three data tables, you can see that none of the time columns start at zero seconds. This is because for each video, the car didn t begin moving until a few seconds into the video. Also, the data tables are of different lengths because with each added weight, the toy car took a different length of time to travel a meter.

3 Graphs of Data 1.2 Position Data for three trials Position (in meters) Time (in seconds) 0g 100g 200g Figure 4 This graph shows the different times of each trial when the car reached the same distance. Velocity (m/s) Velocity Data for three trials V 200 = 0.09t V 100 = 0.4t g 100g 200g Time (in seconds) V 0 = 0.6t Figure 5 This graph displays the different accelerations of my toy car while carrying different weights.

4 Analysis of Data I began this experiment by asking myself one question, When I add different weights to my toy car, how will that affect its movements? Will it travel faster? Will it travel slower? Will it have any effect at all on my toy car? To find some answers, I conducted three trials. For each trial, my toy car was the control variable, and the different weights added to the car were the independent variables. I videotaped the car traveling a distance of 1 meter. The car carried no extra weights for the first trial, a 100g weight for the second, and a 200g weight for the third. After I had a video of each of the trials, I uploaded them onto Logger Pro and plotted points for every third frame of each video. With sets of time, position, and velocity data, I created two graphs. We can see that for both graphs, the points travel downwards (negative slope) instead of upwards (positive slope) as we might expect, and that the y axis scale decreases. This is because my car traveled from right to left in the video. On a regular graph, that would indicate the car traveling a negative distance. It does not affect the data whatsoever; we will just have to analyze the data in a different way. Looking at the x axis on both graphs, we can see that the three different sets of points span different moments in time. They do not all start at the same point. This is because each video could not be taken in the exact same way, so we will have to disregard that factor for this analysis. In Figure 4, we can already see how the different weights affected how much distance my toy car traveled each second. With no added weights, the car was able to travel 1 meter in a little more than one second. While carrying a weight of 100g, the car traveled the same distance in a little less than two seconds. When it carried 200g of added weight, the car traveled 1 meter in more than three seconds. Already, we can see that with greater mass, the toy car travels slower. Also, because I marked every third frame of each video, we can see much more points in the 200g position data than the 0g position data. This means that the car with greater weight required more frames to travel the same distance. Thus, we can prove again that the car travels slower with increased mass. Furthermore, we can see that there is a slight curve at the beginning of each set of points. This shows the toy car s acceleration. As it accelerated, less frames (and thus, less points) were necessary to plot its movements. Covering more distance in less time, the plotted points grew more apart in distance and appear to curve less. Figure 5 shows the acceleration of my toy car for each trial. For each set of data, the points look almost like a line, so this must mean that the velocities increased steadily. We can see that with no added weights, the car had the greatest increase in velocity. With 100g of added weight, it had a less drastic increase in velocity. While carrying 200g of added weight, the increase in velocity was the smallest amongst the three. I came to these three conclusions by looking at the slope of the lines. If the slope is greater, that means its acceleration is also greater. The force of friction between the toy car and the floor increased as greater weights were added to it, thus making it more difficult for the toy car to accelerate. Also, since greater mass indicates greater inertia, this explains why it was more difficult for the car to accelerate during the 200g trial. The inertia of

5 the toy car was much greater, which means that it was more resistant to a change in motion. If I were to conduct this experiment again, I would change one particular factor to make the results easier to understand: I would have the toy car run from left to right on the video, so that the graphs contain lines with positive slopes. Conclusion Newton s first and second laws of motion are closely related to this toy car experiment. His first law, the law of inertia, explains why there is curvature in the position data graph all objects resist change, especially ones with greater mass, so a force was required to accelerate the car. Before it began moving, the car was in mechanical equilibrium because of the zero net force on it, but its state of motion was suddenly changed. When the force acted on the car, the car couldn t immediately accelerate. Therefore, its acceleration was not at a constant rate. The moments in which it took to reach a seemingly steady acceleration are the apparent curves at the start of the lines of points. As for Newton s second law, it tells us that if the mass of an object were doubled, then its acceleration would be halved. Mass is directly proportional to weight, which means that greater mass means greater weight. Because the trials were all conducted using the same amount of force, the trials with heavier weights had a slower acceleration. To sum things up, this experiment was based on comparing the effects that different added weights had on a toy car. The three weights were zero added weight, 100g, and 200g, and the car traveled the same distance by the same amount of force for each separate trial. After assessing the results based on position and velocity graphs, I have come to two conclusions: 1) Greater weight = less acceleration 2) Greater weight = less velocity The way that the variable of weight affected the motion of the car was quite predictable, but I didn t really understand the reasons behind it. After conducting this experiment and consulting sources to find answers, I have gained greater insight into the mechanics of how different weights can affect the motions of a toy car.