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WARM-UP What are the two main categories of forces? WHAT EXACTLY IS A FORCE A force is a push or pull on an object Recall: A force can act though contact Spring, normal, applied, friction, etc A force can act a distance Gravity, magnetism, electrical VECTORS Magnitude and Direction: PROJECTILE MOTION http://www.nbclearn.com/portal/site/learn/scienceof-nfl-football PROJECTILE MOTION Only one force is acting on an object during projectile motion – gravitational force Often air resistance is negligible Object follows a parabolic path PROJECTILE MOTION Another way to define projectile motion is horizontal and vertical motion that is independent of one another. Why is that important? It means we can look at each direction individually HORIZONTAL MOTION No external forces acting in horizontal direction. This means: constant velocity VERTICAL MOTION Gravitational force will pull the object down. Direction of this force is from the direction of acceleration, which is directed down. Eventually, the projectile will reach a vy = 0 m/s. This occurs at the maximum vertical height. After this, the ball begins to accelerate in the downward direction. VERTICAL MOTION Increasing velocity in downwards direction: PUTTING IT ALL TOGETHER The path of the projectile cannot change its path without introducing a new force. Training must prepare an athlete to accurately set the projectiles path just before release. NBC – Nick Goepper & the Physics of Slopestyle Skiing http://www.nbclearn.com/science-and-engineering-ofthe-2014-olympic-winter-games PROJECTILE RAMP CHALLENGE Day 2 Projectile Motion Challenge Remember: Your ramp must be able to be set at 4 different angles: 15o, 30o, 45o, 90o. Once you have finished building your projectile launcher, you will measure its horizontal distance at each angle. You will need to make 3 different measurements at each angle. Ramp Challenge Per Group: Ramp Sketched design of your ramp Per Person: Data Table Answers to questions Pre-Lab Question: Which angle do you predict to have the greatest horizontal displacement? Questions Did your final design differ from your initial sketch? If so, explain the difference AND make a sketch of your final design. Which angle launched the marshmallow the farthest horizontal distance? Which angle do you think produced the greatest vertical height? What other variables could have been introduced during this experiment? If your results showed an angle besides 45 degrees for farthest distance, then what could have been your error? 3 CONCERNS WITH PROJECTILES Time of flight Peak height Horizontal displacement Which sports are concerned with time of flight? Peak height? Horizontal displacement?. SIMULATION http://phet.colorado.edu/sims/projectilemotion/projectile-motion_en.html Think of our three major concerns with projectile motion Time in flight Peak height Horizontal displacement TIME IN FLIGHT Physics Depends on: Sports Gymnastics Figure Skating Ski jumping Snowboarding (half-pipe) Initial vertical velocity Initial vertical position Optimal angle of projection: 90o Above 45o Maximize Time: Minimize Time: Volleyball spike Tennis smash PK kick – soccer Baseball throws PEAK HEIGHT Physics Depends on: Initial height Initial vertical velocity Optimal angle of projection: 90o Greater than 45o Larger angle = larger vertical velocity Sports High Jump Volleyball Basketball HORIZONTAL DISPLACEMENT Physics Depends on: Initial horizontal velocity Time in flight: Initial vertical velocity Initial height Optimal angle of projection: Sports Shot put Discus throw Long jump Baseball hit 45o there are equal x & y components Smaller angles are required if initial height is present. Harder to produce vertical motion than horizontal Imagine a bowling ball – is it easier to roll it horizontally or throw it up in the air? Applications In Sports Golf – Long Irons (1,2, 3) have a shallow angle on the club face. They are designed for distance. Short irons (7, 8, 9, wedge) have steeply angled faces to give height and “stopping” ability when the ball lands. Biomechanics Speed of release can be maximized in order to gain distance or time in flight by applying biomechanical principles such as transfer of momentum, sequencing and lengths of levers. By driving with Legs torso shoulder arm hand. The body acts like a whip imparting tremendous force to the ball. Winter Olympics Project Exit Ticket What force(s) is/are acting on an object during projectile motion? What implications does projectile motion have on sports, knowing that you can’t change the projectile’s path once it is in the air?