# Pendulums

This week, we’ve been learning all about pendulums. Pendulums are weights that are hung from a fixed point, for example, a chandelier and a wrecking ball would be pendulums. We did 4 controlled experiments, which are experiments where 1 variable, which is something that could change the results of the experiment, is changed, while the rest remain controlled. The variable that we change becomes the independent variable in the experiment. So what is a dependent variable? A dependent variable is the result of the experiment. A trick I use to remember this is that the dependent variable depends on the independent variable. For example, if I changed the mass of the bob, which is the weight at the bottom of the pendulum, the mass of the bob would be the independent variable, while the rest are controlled variables.

The first experiment was having a penny hung to a 38 centimeter string, and releasing it at a 90 degree angle, and counting how many cycles it makes in 15 seconds, the result after 32 trials (tests) were 12 cycles, so each cycle had a period, which is the time it takes to complete 1 cycle, of 1.25 seconds.

The second experiment was changing the bob’s mass, by exchanging the penny with a quarter. But still using a 38 centimeter string, and releasing it at a 90 degree angle and using 15 seconds, the results after another 32 trials, were still 12 cycles. So the bob’s mass didn’t affect the results.

The third experiment was changing the release place, we changed it to releasing at a 45 degree angle, and reused the penny and kept the length as 38 centimeters. The results were the same, so we came to the conclusion that most of the variables don’t affect the results, but we still had one experiment to do.

The last experiment had each group having 2 pendulums with strings of different lengths. The results were that the longer the length of the string the fewer the cycles, and the shorter the length of the string the more the cycles. We then made 2 graphs, one pictograph, and one coordinate graph. I thought that the length would not effect the amount of cycles, but I was wrong. Here are the graphs for you to see.

And here are some pictures from the experiments!