![]() ![]() To hit the ball correctly we need enough time for a proper stroke. Vertical velocity of the free falling ball will then simply be:Īny object falling to the ground accelerates each second by 9,81 m/s 2 and its distance travelled grows with the time squared. Our equation will be markedly simpler as the initial velocity of the ball v p equals zero: Let us now analyze the motion of a ball dropped to the ground. This equation allows us to calculate the vertical position of the projectile y k at the end of the time interval Δt, given its initial velocity v p and the length of that time interval. And do we know anything about the projectile’s position? The final position can be calculated as: We can see that the vertical velocity of the projectile is in direct proportion to the time the projectile spent in the air. The following equation allows us to calculate the instanteous vertical velocity of a projectile at the end of any time interval Δt, given its initial velocity and the length of that time interval. Projectile motion can be described with equations that relate velocity, displacement, acceleration, and time. When neglecting friction (such as air resistance), projectiles always move in vertical direction either in uniformly decelerated motion (if going up) or uniformly accelerated motion (if falling down) with the gravitational acceleration of 9,81 m/s 2. In the previous chapter we already mentioned that gravitational acceleration g equals roughly 9,81 m/s 2 and is oriented downward. In such cases only gravitational force acts on a projectile. Sometimes the resistance is very small and can be neglected. Two forces always act on such projectiles: A number of objects in sport and physical exercise can be considered to be projectiles: javelin, shot, discus, but also human body itself. “Projectile” is a term used in sport and physical exercise for any body that is launched, thrown, or shot into air in any direction, or simply dropped to the ground. The condition here is that the resulting external force acting on the body is constant and non-zero. Such motion is called uniformly accelerated motion. There are many situations in both everyday life and sport activities in which bodies move with constant acceleration. ![]()
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