Principles about Projectiles in Sports

Projectiles in sports include objects and athletes in flight as a result of throwing, batting, kicking, and jumping. If you are a thrower, long jumper, basketball player, or any other athlete whose sport involves objects in flight, these principles about the effects of force on angle, height, impact, and spin can help you. Understanding these effects offers direction for developing sound technique for related sport skills.

Principles about Forces that Affect Flight

1. The force pushing an object determines its direction and rotation in flight. For example, a curve ball travels more slowly than a straight ball due to the force that is generated off center into the spin, as well as the retarding effect of air friction.

2. The force of gravity has a downward effect on flight as soon as contact with the driving force (e.g., a bat, thrower's hand) is broken. The weight (mass), upward force, and air resistance determine how quickly an object (e.g., a javelin, ball, or springboard diver) will fall.

3. As speed increases, air resistance has a greater retarding effect on an object in flight. For example, a javelin or discus should be released at an angle of tilt that exposes the least surface area in flight in order to maximize throwing distance.

Principles about Angle and Height of Projectiles in Sports

4. To acheive maximum distance, the optimum angle of projection is 45 degrees, assuming that the beginning and ending points are at the same level. For example, the angle of release for a shot put is closer to 42 degrees or less because it is released well above the level of the landing area.

Animated Jump in Air 5. The time in flight depends upon the height it attains. For example, a springboard diver attempts to project himself high in the air in order to allow time to complete the desired airborne movements.

The speed at take-off has an impact on the height or distance athletes (projectiles in sports) jump. Training to build power fitness, or the combination of speed and strength, improve jumping time in the air.

Principles about Impact on Objects

6. The angle of rebound of a projectile equals the angle at which it approaches a surface (angle of incidence), but can be affected by irregular shapes, elasticity, and spin. For example, a basketball rebounds off a backboard at the same angle at which it approaches, unless it is partially deflated or a player puts spin on it.

7. When both an object and the striking surface are moving, the momentum with which the object will rebound equals the momentum of both, minus the momentum retained by the striking object. For example, the striking force of a bat on a ball is determined by the momentum of both objects. A fast-moving ball will rebound with greater velocity than a slow-moving ball, provided the bat can overcome the inertia of the ball.

Principles about Spin on Projectiles in Sports

8. An object propelled without spin tends to waver due to air resistance against an irregular surface, but a small amount of spin produces stability. For example, a volleyball served with a slight spin follows a true course of flight.

9. An object spins in the desired direction when the striking implement is drawn across it in the intended direction. For example, tennis players attempt to stoke the ball with a forward-upward motion in order to impart topspin.

10. The effects of spin on a ball landing on a horizontal surface as follows:

A. Topspin causes a lower angle of rebound, a longer bounce, and more roll.

B. Backspin causes a higher angle of rebound, a shorter bounce, and less roll.

C. Sidespin causes the angle of rebound to change toward the direction of the spin.

These are only a few examples of how athletes can apply mechanical principles about projectiles in sports to improve performance.

Pages related to projectiles in sports:

Newton's Laws of Motion

Mechanical Principles

Principles of Force

Stability Principles


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