Timing the period

Students often ask whether they need to count from when the weight is at the bottom of the cycle or whether the top is fine. I hope the graph of the sine function up top tells you the answer. The period is the time it takes for the object to return to the initial state, whatever that initial state is. All three T measurements on that graph are legitimate. So measure the state that's easiest for you.

 

Also on this photo is a description of the graph I'd like, with T in seconds on the y axis and m in kg on the x axis

Done