7 A particle is projected with speed \(65 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) from a point on horizontal ground, in a direction making an angle of \(\alpha ^ { \circ }\) above the horizontal. The particle reaches the ground again after 12 s . Find

1. the value of \(\alpha\),
2. the greatest height reached by the particle,
3. the length of time for which the direction of motion of the particle is between \(20 ^ { \circ }\) above the horizontal and \(20 ^ { \circ }\) below the horizontal,
4. the horizontal distance travelled by the particle in the time found in part (iii).