1 A small ball is projected with speed \(16 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle of \(45 ^ { \circ }\) above the horizontal from a point on horizontal ground. Calculate the period of time, before the ball lands, for which the speed of the ball is less than \(12 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).