The place kicker on a football team kicks a ball from ground level with an initial speed of 8.40 m/s at an angle of 21.0° above the horizontal. How long is the ball in the air, in seconds, before it lands on the ground again? You may neglect air resistance.

Answer:See below Explanation:Vertical component of the kick-off velocity is  8.4 sin21° = 3.01 m/s Find the time-point where vertical velocity = 0   the ball is in the air for twice this long  ( as it still has to fall back down to the ground) vf = vo + at 0  = 3.01 m/s   - 9.81 t     shows t = .307   twice this is .614 sec     ( what a sorry kick !)