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A drop kick. The most important skill and ability in the game of Rugby. A drop kick is more important than a tackle, a hit, a scrum and even placing the ball on the ground to score a try. Without a drop kick, the game of Rugby can not even be played. A drop kick is what starts the game. As well as starting the game so that it can be played, a drop kick also allows teams to gain extra points. Throughout a game of Rugby, at any moment a player can perform a drop kick. If the player gets it through the up rights, then their team will receive three points.
By knowing that the ball traveled twenty-five meters in two seconds at an angle of forty-eight degrees, we can determine the balls maximum speed, it's acceleration and the maximum height of the ball.
Kinematics :
Because the ball is travelling at an angle of forty-eight degrees, to find the initial velocity, which is equal to the final velocity because of its parabolic motion. We have to find the vertical and horizontal components of the initial velocity :
Initial Vertical Velocity :
Viy = Vi Sin θ
= Vi Sin 48°
= 0.74 Vi m/s
Because the initial vertical velocity is equal to the final vertical velocity :
Vfy = - 0.74 Vi m/s
a = - 9.8 m/s²
Knowing that the final velocity is equal to the initial velocity, we can find the initial velocity of the ball :
a = - 9.8 m/s² a = Vf - Vi / Δd
Vi = 0.74 Vi m/s Vfy = Viy - a Δd
Vf = 0.74 Vi m/s - 0.74 Vi m/s = 0.74 Vi m/s - (9.8 m/s²) (2.5 s)
Δd = 2.5 s 1.48 Vi m/s = 24.5
Vi = 16.55 m/s
Finding the vertical velocity of the ball will allow us to find out the maximum height of the ball as well :
Vertical Velocity : Maximum Height using the Vertical Velocity :
Viy = 0.74 Vi Δt = 1.25 s Δd = Viy Δt + (0.5) a (Δ)²
= 0.74 (16.55 m/s) Viy = 12.2 m/s = (12.2 m/s) (1.25 s) + (0.5) (- 9.8 m/s²) (1.25 s)²
= 12.2 m/s ag = - 9.8 m/s² = 9.125 m
Δd = ?
Forces :
When looking at the Free Body Diagrams of the kick, we can understand why the ball goes through a parabolic motion :
Free Body Diagram of leg : Free Body Diagram of ball :
By knowing that the ball traveled twenty-five meters in two seconds at an angle of forty-eight degrees, we can determine the balls maximum speed, it's acceleration and the maximum height of the ball.
Kinematics :
Because the ball is travelling at an angle of forty-eight degrees, to find the initial velocity, which is equal to the final velocity because of its parabolic motion. We have to find the vertical and horizontal components of the initial velocity :
Initial Vertical Velocity :
Viy = Vi Sin θ
= Vi Sin 48°
= 0.74 Vi m/s
Because the initial vertical velocity is equal to the final vertical velocity :
Vfy = - 0.74 Vi m/s
a = - 9.8 m/s²
Knowing that the final velocity is equal to the initial velocity, we can find the initial velocity of the ball :
a = - 9.8 m/s² a = Vf - Vi / Δd
Vi = 0.74 Vi m/s Vfy = Viy - a Δd
Vf = 0.74 Vi m/s - 0.74 Vi m/s = 0.74 Vi m/s - (9.8 m/s²) (2.5 s)
Δd = 2.5 s 1.48 Vi m/s = 24.5
Vi = 16.55 m/s
Finding the vertical velocity of the ball will allow us to find out the maximum height of the ball as well :
Vertical Velocity : Maximum Height using the Vertical Velocity :
Viy = 0.74 Vi Δt = 1.25 s Δd = Viy Δt + (0.5) a (Δ)²
= 0.74 (16.55 m/s) Viy = 12.2 m/s = (12.2 m/s) (1.25 s) + (0.5) (- 9.8 m/s²) (1.25 s)²
= 12.2 m/s ag = - 9.8 m/s² = 9.125 m
Δd = ?
Forces :
When looking at the Free Body Diagrams of the kick, we can understand why the ball goes through a parabolic motion :
Free Body Diagram of leg : Free Body Diagram of ball :
Energy :
Because the ball goes through a parabolic motion, the amount of energy at the being of the motion is the same as the amount of energy at the end of the motion due to energy conservation :
Because the ball goes through a parabolic motion, the amount of energy at the being of the motion is the same as the amount of energy at the end of the motion due to energy conservation :
Here we can see the video of a drop kick being performed to gather the information :
From what we have learned, the maximum speed of the ball is when the ball is initially kicked and right before it hits the ground at 16.55 m/s. As well, the maximum height of the ball is 9.125 m. As well, the ball follows a parabolic projectile path and has the same amount of energy from the initial kick to the ball hitting the ground.