Đang tải... (xem toàn văn)
The physics of basketball john j fontanella tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập lớn về tất...
[...]... example, in figure 1.1, the total speed of the left surface of 14 The Physics of Basketball the basketball is greater than the total speed of the right surface of the ball That is because the left surface is moving downward relative to the center of the ball which is moving downward Consequently, the total speed of the left surface is the sum of the two speeds On the right of the ball, the surface is moving... if the basketball weren’t there, 10 The Physics of Basketball that portion of the air would be in equilibrium on average Since there is a downward force of gravity on that portion of the air, there must be an equal and opposite force upward on that portion due to the rest of the air The upward force due to the rest of the air is the buoyant force The same upward buoyant force is exerted on the basketball. .. reduce the effect (force) of gravity, the shape of the trajectory of a thrown basketball under the influence of only gravity and the buoyant force would be the same as if it is only affected by gravity The other two main forces of the air on the ball do change the shape of the trajectory By the way, the reason that a helium balloon rises is that its weight is less than the buoyant force Since the upward... center of the basketball in figure 1.1 since that’s close to where the total (net) gravitational force on the ball appears to act, the so-called center of gravity As we’ll see, sometimes it’s not convenient to draw the tail of the arrow at the origin of the force The strength of the force of gravity on the ball is also known as the weight of the ball, so we know that the strength of the force of gravity... basketball by the rest of air, because the rest of the air doesn’t know or doesn’t care what occupies the volume We can calculate the upward buoyant force because we can calculate the weight of the displaced air We know the volume of the displaced air since it is equal to the volume of a basketball, Vbasketball We also know the density of air, ρ air Consequently, ρ airVbasketball is the mass of the displaced... on the ball, yet there is no acceleration because the velocity is not changing The reason that the acceleration is zero is that the total (net) force on the ball is zero The total (net) force on the ball is zero because, in addition to the downward force of gravity, there is an upward force on the ball when it is sitting on the floor, 6 The Physics of Basketball the force of the floor on the ball The. .. near the surface of the Earth The Final Four 7 The direction of the force of gravity on the ball is downward since the Earth pulls the basketball downward When drawing vectors, I like to put the tail of the arrow at the point where the force is applied That would make the vector appear to originate where the force is applied or appears to be applied The tail of the arrow Fgravity is drawn at the center... per kilogram2), mbasketball is the mass of the basketball, mEarth is the mass of the Earth and REarth is the radius of the Earth We are assuming that the basketball is a distance REarth from the center of the Earth Equation (1.2) can always be used to calculate the force of gravity Plugging values for G, and the mass and radius of the Earth into equation (1.2), we get Fgravity = mbasketball times 9.8... drag force For the speeds typical of a basketball game the air drag force on a basketball varies as the square of the speed, υ The drag force is also proportional to a special area, A This is the area that the basketball “sweeps out” as it moves through the air Finally, the drag force is proportional to the density of the air The more dense the air, the more difficult it is for the basketball to make... case is when gravity is the only force on an object near the surface of the Earth Since the force of gravity is proportional to the mass of the object, the acceleration does not depend on the mass of what is falling This implies that the acceleration of either a men’s or a women’s basketball falling under the influence of only gravity would be 9.8 m/s2 That would be the case if a basketball were falling . w0 h0" alt="" The Physics of Basketball This page intentionally left blank The Physics of BASKETBALL John J. Fontanella The Johns Hopkins University Press Baltimore © 2006 The Johns Hopkins. Data Fontanella, John (John J. ), 1945– The physics of basketball / John J. Fontanella. p. cm. Includes bibliographical references and index. ISBN 0-8018-8513-2 (hardcover : acid-free paper) 1. Physics. . Coach of the Year of the National Association of Intercollegiate Athletics. He was 1974 Coach of the Year of the National Collegiate Athletic Association in the East while at the University of Pittsburgh.