Here is a screenshot of the question: http://prntscr.com/ao79xi
The first part is fairly straight forward, I worked out the time period by doing the following calculation.
T = no. of oscillations/time taken, 42/15= 2.8 Seconds
However in the second part of the question I am incorrect, I did the following:
Since it is asking us for her kinetic energy as she passed through the lowest point I was assuming that velocity is max, so I did this:
Vmax = 2*Pi*f*A
We are provided with the amplitude so with the given information I calculated Vmax to be 0.56m/s, then inputted these values in the kinetic energy formula, 1/2*m*v^2, which gave me a value of 2.82 J, I do not understand why this is incorrect? In the mark scheme they said that Ek = mgh, which gives the kinetic energy of the girl at the lowest point. (44 J). Thanks in advance!
...with these A Level results?