Physics in Your Life Softball Alexa Geiswhite Period

Physics in Your Life: Softball Alexa Geiswhite Period 11 January 22, 2008

Introduction n The objective in softball is to transfer as much energy to the ball as possible. n As a projectile, the speed of the ball is affected by faster arm speed. § n The velocity of the ball will equal that of the instantaneous vector exerted by the arm at the last second of its being held. After the ball is released, the preferred angle of swing would be to hit the ball just below its centerline.

Ball Spin n Bottom Spin (backspin) – to your benefit; creates lift. n Bernoulli Effect – more air flowing over the top of ball and less air pressure than on the bottom, which creates lift. n Top spin – causes the ball to arc towards the ground. n Backspin creates more lift and a greater distance.

Size Doesn’t Matter n Center of Percussion (sweet spot) - vibration is decreased and ball speed is increased to its maximum. n n n No net force is felt by the player By changing the MOI (center-of-mass) and balance point, the location of the center-of -percussion also changes Relative to the 6 inch pivot point on the handle. (Pendulum Effect) Does bat weight affect the swing? Type Length Slow Pitch 33” – 34” Fast Pitch 32" - 34" Baseball 31” – 34” Type Weight Slow Pitch 26 oz. – 30 oz. Fast Pitch 23 oz. – 28 oz. Baseball 28 oz. – 31 oz. Bat Swing Speed 20. 5 mph (9. 2 m/s) 27. 3 mph (12. 1 m/s) 34. 3 mph (15. 3 m/s) 41. 0 mph (18. 3 m/s) 47. 9 mph (21. 4 m/s) Batted Ball Velocity 62. 0 mph (27. 7 m/s) 68. 8 mph (30. 7 m/s) 76. 2 mph (34. 0 m/s) 83. 8 mph (37. 4 m/s) 91. 4 mph (40. 8 m/s) • Ideally, swinging a heavier bat with the same speed as a lighter bat would produce maximum speed/distance. Bat Weight 20 oz (0. 57 kg) 25 oz (0. 71 kg) 30 oz (0. 85 kg) 35 oz (0. 99 kg) 40 oz (1. 14 kg) Batted Ball Velocity 68. 5 mph (30. 6 m/s) 73. 0 mph (32. 6 m/s) 76. 2 mph (34. 0 m/s) 78. 6 mph (35. 1 m/s) 80. 4 mph (35. 9 m/s)

Moment of Inertia n Swing speed is directly related to the moment-of- inertia (swing weight) which is linked to both the weight and length of the bat. n Difference between bat weight and swing weight. n When the bat and ball are in contact, the force exerted by the player is the force needed to swing the bat. n Because of this, momentum is not constant.

When Ball Meets Bat n The Trampoline Effect: n Ball/bat compresses, stops, expands • • bat compresses ball bends/compresses bat n An average force of 8, 000 lbs act within milliseconds of contact on the bat. n Ration of incoming to outgoing velocity: coefficient of restitution (COR). Ball loses about 80% of its stored energy. n Kinetic energy is lost after contact to friction forces n Transferred as vibrational energy to the bat Force exerted by a baseball compared to that of a soft ball (1: 37 -2: 50)

Aluminum vs. Wood n In the field, it’s accepted by all n n that aluminum bats perform better than wood. Batted ball speed was about 4 mph faster Aluminum bats have a larger center of percussion Though aluminum bats are heavier, the balance point is closer to the handle making them easier to swing. Wooden bats tend to break much more easily.