Motion in Sport, Projectiles, Friction, COR - ppt download

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Motion Linear Motion . (Translatory motion) The sprinter runs from A to B. Curvilinear Motion Most jumps are along a curved line. The pathway of the runner is a straight line BUT it happens because of angular motion of the joints of the limbs. Linear motion can be considered in terms of quantities of: Distance – displacement – velocity – acceleration and therefore force. REMEMBER A body’s inertia is it’s resistance to change in motion. With linear movement, mass is the only measure of that inertia. IN OTHER WORDS The greater the mass, the greater the resistance to change, and therefore the greater the inertia. EDU4SBM Sports Biomechanics
Lecture Week 5. Motion in Sport, Projectiles, Friction, COR. EDU4SBM Sports Biomechanics.
The sprinter runs from A to B. Curvilinear Motion. Most jumps are along a curved line. The pathway of the runner is a straight line BUT it happens because of angular motion of the joints of the limbs. Linear motion can be considered in terms of quantities of: Distance – displacement – velocity – acceleration and therefore force. REMEMBER. A body’s inertia is it’s resistance to change in motion. With linear movement, mass is the only measure of that inertia. IN OTHER WORDS. The greater the mass, the greater the resistance to change, and therefore the greater the inertia. EDU4SBM Sports Biomechanics.
The thrown object is called the projectile. Its path is called the trajectory. We will not consider air resistance. Without air resistance, the projectile will follow a parabolic trajectory. This is a two dimensional problem. Therefore, we will consider x and y directed displacements, velocities, and accelerations. EDU4SBM Sports Biomechanics.
Golf ball. Basketballs. Javelin. Ski jumping. Diving. Trampoline. Archery. Soccer. Football. Cricket. EDU4SBM Sports Biomechanics.
Angle of release. Speed of release. Height of release. Gravity. Spin. Air resistance. See java demo. EDU4SBM Sports Biomechanics.
change occurs only in the vertical direction due to the influence of gravity, while the horizontal component of the velocity will not change. (This is not quite true, there will be a very small slowdown in the horizontal direction due to air resistance). EDU4SBM Sports Biomechanics.
The original conditions are the size of the velocity and the angle above the horizontal with which the projectile is thrown. Velocity = 40 m/s. 35 degrees. Velocity = 40 m/s. Angle = 35 degrees. EDU4SBM Sports Biomechanics.
Horizontal component. Vertical component. V (vert) V (horiz) EDU4SBM Sports Biomechanics.
a (horiz) = 0. There is no force acting in the horizontal direction once the projectile has been launched. a (vert) = g or 9.8 m/s2. Gravity is a force acting on the projectile. The projectile will accelerate under the influence of gravity, so its vertical (x) acceleration will be downward, or negative, and will be equal in size to the acceleration due to gravity on Earth. There will be no acceleration in the horizontal (x) direction since the force of gravity does not act along this axis. EDU4SBM Sports Biomechanics.
At the top of the trajectory the y, or upward, velocity of the projectile will be 0 m/s. The object is still moving at this moment, but its velocity is purely horizontal. At the top it is not moving up or down, only across. velocity (final) = velocity (initial) + at. In the vertical direction. velocity(final) = 0. velocity(initial) = a = t = velocity (final) = velocity (initial) + at. EDU4SBM Sports Biomechanics.
Here you need to find the displacement (D) in the y direction at the time when the projectile is at the top of its flight. D = vt + ½ a t2. V = 22.9 m/s. T = 2.33 sec. A = -9.8 m/s2. D = vt + ½ a t2. EDU4SBM Sports Biomechanics.
D = vt + ½ a t2. This time we are working in the horizontal direction. V = 32.8 m/s. a = 0 m/s2. t = 2.33 sec (X 2 for total journey) D = vt + ½ a t2. EDU4SBM Sports Biomechanics.
Friction EDU4SBM Sports Biomechanics
grass, moving the ball from one side of the field is much harder than moving an ice hockey puck across an ice rink due to a force called friction. There is more friction on a coarse, grassy surface than on the slick surface of an ice rink due to the amount of resistance. Field hockey player, therefore, must hit the ball with a great amount of force to send it across the field, whereas ice hockey players can easily send a puck gliding across the rink. EDU4SBM Sports Biomechanics.
If you have ever bowled, you know that after rolling the ball it continues to move across the alley until it comes into contact with the pins. After being put into motion, the bowling ball will remain in motion until friction eventually slows it down. If the bowling alley never ended would the ball keep rolling forever No! As a result of friction (an outside force) the ball will eventually stop. EDU4SBM Sports Biomechanics.
Sportsmen reduce drag by using specialised techniques, equipment or clothing. Streamlining reduces form drag. Form drag results from the suction-like force created between the positive pressure zone on the leading edge and the negative pressure on the trailing edge when turbulence is created by moving through the air or water. The effect of streamlining is a reduction in the turbulence created at the trailing edge of a body in a fluid. EDU4SBM Sports Biomechanics.
Lift Force. Direction of fluid flow. Although LIFT implies that the force is directed upwards – it may assume any direction as determined by the direction of the fluid flow and the orientation of the body. The angle of attack is the angle formed between the primary axis of a body and the direction of the fluid flow. Spin also generates lift force e.g. magnus effect on a backspinning dimpled golf ball. Lift force. EDU4SBM Sports Biomechanics.
To find the coefficient of restitution in the case of a falling object bouncing off the floor, or off a racquet on the floor, use the following formula: c = coefficient of restitution (dimensionless) h = bounce height. H = drop height. EDU4SBM Sports Biomechanics.
It can also be calculated this way using kinetic energy if we know the velocities before and after collision. M = mass. V = velocity. V = 4 m/s. M = 0.3 kg. KE = _____________. V = 5 m/s. M = 0.3 kg. KE = _____________. EDU4SBM Sports Biomechanics.
The USGA has adopted limits of on the coefficient of restitution a given clubface may have as part of its effort to define the boundaries of technology in the game. EDU4SBM Sports Biomechanics.