4 A particle \(P\) is projected with speed \(50 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle of \(30 ^ { \circ }\) above the horizontal from a point \(O\) on a horizontal plane.
- Calculate the speed of \(P\) when it has been in motion for 4 s , and calculate another time at which \(P\) has this speed.
- Find the distance \(O P\) when \(P\) has been in motion for 4 s .