The force exerted on the rugby ball by Francois Steyn (The longest rugby conversion kick)

Tinashe Nyanhete

Steyn’s record 66m kick.  http://www.youtube.com/watch?v=muI0ULBSWmw

Horizontal distance (x) = 68m

Time of flight of ball (t) = 4s

V_xo = x/t = 68m/4s =17m/s

V_y0 = gt = 9.8ms^-2 * 4s = 39.2m/s

V = 43m/s

The approximate change in velocity of the ball after Francois struck the ball was 43m/s, which is higher than the normal reported value of 30m/s, since the ball travelled the highest ever recorded horizontal distance for a conversion kick.

Now to determine the force on the ball due to the kick (Use Newton’s 2^nd and 3^rd laws):

F = ma, and action = -reaction (Force exerted on ball = force exerted on the foot by the ball)

F = mv/t

Ft = mv, where t – time of contact between the foot and the ball; v – change in velocity of ball; m – mass of ball

Time of contact with the ball = 0.013s

Mass of ball = 0.44kg

Change in velocity of ball = 43m/s

Therefore, F = mv/t = 1455N

This is larger than the normal estimated force of 1015N, which explains why Francois Steyn’s ball travelled a record distance.

Reference: http://www.coachesinfo.com/index.php?option=com_content&id=228&Itemid=147