[填空题]
An object moves in a sv v lzc)jl5;1ltraight line sut p b*/z08r*e0rmsky2uwhs +i;f,xw0mjm .jbch that its velocity, v \mathrm{~m} \mathrm{~s}^{-1} , at time t seconds, is given by
1. Find the value of t , for t>0 , when the object is instantaneously at rest.
t= s.
The object returns to its initial position at t=T .
2. Find the value of T . Give your answer correct to three significant figures.
T≈ s.(one decimal place)