Question

A spring is oscillating vertically according to the equation y=3cos(2t-pi) where y is the displacement in feet and t is time in seconds. At what time will the spring be 2 ft. high? Round your answer to the nearest tenth.

Answer 1

we have the equation

`y=3cos(2t-pi)`

For y=2 ft

substitute in the given equation

`\begin{gathered} 2=3cos(2t-p\imaginaryI) \\ cos(2t-p\mathrm{i})=(2)/(3) \end{gathered}`

Solve for t

using a calculator

2t-pi=0.84

2t=0.84+pi

2t=3.98

t=1.99 -----------> round to one decimal place

t=2.0 sec

The answer is option C