When a pendulum swings 35degree from the vertically, the weight moves 15cm horizontally and 5.3 vertically. The length of the pendulum?

1 answer

sketch the sector to the right of the vertical.
Label the centre as C, the end of the swing as A and the point on the horizontal hitting the pendulum B
So AB = 15 cm
we can find OA
tan 35° = 15/OA
OA = 15/tan35 = 21.422...

so the length of the pendulum is 21.422 + 5.3 = 26.722 cm