What comes to mind when you hear the word physics? Perhaps you picture a bright green baseball field. Maybe you envision a pitcher throwing a baseball to home plate. Possibly you hear the crack of a bat hitting a ball and the roar of the crowd. That wasn't what you were thinking? Maybe it should be. After all, physics and baseball go hand in hand.
For year, many people thought that a curveball was just an optical illusion. Physicist, however, have long known that spinning ball curves in flight. In fact, Isaac Newton wrote a paper on this subject back in 1671. Then, in 1852, the German physicist Gustav Magnus investigated the topic further.
According to Magnus, a ball moving through air interacts with thin layer of air known as the boundary layer peels away from the surface of the ball. This creates a region of low pressure, known as a wake, behind the ball. The difference in pressure between the front and back of the ball creates a backward force on the ball. This slows its forward motion. This is the normal air resistance, or drag, on the ball.
If the baseball is spinning as it moves, the boundary layers separate at different points on opposite sides of the ball. It separates further upstream on the side of the ball that is turning into the airflow. It separates further downstream on the side of the ball turning backward. As a result, the air flowing around the ball is deflected slightly sideways. This results in an uneven, or asymmetrical, wake behind the ball. The effect is a pressure differences across the ball. The resulting lateral force pushes the ball sideways. The lateral force, which is at right angles to the forward motion of the ball, is known as the Magnus force.
The strength of the Magnus force depends on how fast the ball spins and the forward speed of the ball. The faster the spin and speed, the greater the strength of the Magnus force.
The Magnus force is also proportional to the density of the air. This explains why pitchers face a greater challenge at high altitude arena because the air is thinner. The drag on a baseball is therefore less than in an area closer to sea level. Pitches curve less, which makes it easier for batters to hit them. Scientist calculates that a ball curves is about 25 percent less in high altitude than in sea level arena.
The stitches on a baseball play a part in its motion. They gather up air as the ball spins. In this way, they increase the thickness of the boundary layer. They also allow the pitcher to grasp the ball is such a way it can spin. This combination increases the Magnus force.
The direction of the Magnus force depends on the direction of spin. By controlling the direction of the spin, a pitcher can make the Magnus force point in any direction, if, for example, the pitcher gives the ball a clockwise rotation, the ball will experience a leftward force from the pitcher's perspective. This will cause the ball to curve away from the right-hand batter. A ball with a counter clockwise rotation will curve in the opposite direction.
A baseball can be made to drop downward as well. A thrown ball has a natural downward curve due to the force of gravity. If the pitcher gives the ball topspin, the Magnus force will act toward the ground. This cause causes the ball to curve more sharply toward the ground. This is known as a breaking ball.
If, instead, the ball is given a backspin, the Magnus force would have to be greater than the weight the weight of the ball. The spin required to produce a force of this magnitude is greater than can be achieved by pitching a ball. Therefore, a ball with backspin does not actually rise, but it falls less than the batter expects it to. Technically, there is no such thing as a rising fastball. This is a bit of an illusion.
When a ball is hit by a bat, the momentum of the bat is transferred to the ball. As the ball flies away, it is affected by a drag and gravity. In an ideal situation, the combination of these forces causes the ball to follow a parabolic path. The horizontal distance the ball travels depends on the initial velocity and the angle at which it is hit.
If the body is thrown up in air making an angle with the horizontal , it is called a projectile. And the motion associated with the projectile is called as projectile motion The path followed by a projectile is called its trajectory, which is directly influenced by gravity.
The components v0x and v0ycan be found if the angle θ0 is known:
v0x = v0cos θ0 and v0y = v0sin θ0
The horizontal motion and the vertical motion are independent of each other; that is, neither motion affects the other.
Since there is no acceleration in the horizontal direction, the horizontal component of the velocity remains unchanged throughout the motion.
The vertical motion is the motion of a particle in free fall. Equations for free fall apply. For example, . Other useful equations for the vertical y-axis are vy = v0sin θ0 − gt, and .
Eliminating t between the following two equations, x − x0 = (v0cos θ0)t .
When a batter hits a ball, he or she feels a vibration as the bats makes contact with the ball. There is one spot on the bat, however, where the vibrations is reduced to the point that the batter does not feel it. If the ball hits this spot, known as the sweet spot, the batter is almost unaware of the collision. If the ball hits far from the sweet spot, the jarring of the hands can be almost painful. The sweet spot is the point of contact that will make the ball travel the farthest.
The sweet spot results from the vibrations of a bat. To understand this, think about what happens when a spring is pushed down and let go. The spring vibrates or oscillates, back and forth. If enough force is exerted on the bat, it will oscillate as well.
The oscillation of a bat can be described by a wave. Like all natural objects, a bat has a resonant frequency. This is the frequency that will produce the greatest amplitude in the wave. A bat is not symmetric. Hitting a bat at different places will result in different frequencies and amplitude.
When a bat is hit, two waves are produced. One wave is produced when the ball strikes the bat. The other is produced when the ball leaves the bat. At antinodes, the waves meet constructively. This means they add together. If the ball hits the bat at the antinode, it will cause the greatest vibration on the bat. The bat will vibrate so much that it will sting or even break. Antinodes are at the head and mid-point of the bat.
The sweet spot is located about 17cm from the end of the barrel of the bat. It is sometimes known as the "fat part" of the bat because it is the thickest part of the bat.
How does this explain why the ball travels farthest when it collides with the sweet spot? The more the bat oscillates, the more energy that is wasted. The maximum output of the bat results when there are no oscillations. This occurs at the sweet spot.