Answer:
[tex]\text{(a)}\\\text{Given that period of a pendulum can be represented by}:\\P=2\pi \sqrt \frac{l}{g} \\\text{Plugging in values:}\\\frac{0.85}{2\pi }=\sqrt\frac{l}{g}\\\text{Square both sides:}\\(\frac{0.85}{2\pi })^{2}g=l\\\text{Answer }:0.179m \text{ or } 17.9cm\\[/tex]
[tex]\text{(b)}\\\text{Divide 150 by 60, to convert to seconds}\\\text{Invert 2.5/1 to 1/2.5}\\\text{And you get: }0.4\frac{seconds}{beat}[/tex]
