Exam 1 - Projectiles in Sport & Linear Kinematics 2 Flashcards
Projectiles
anything in motion and airborne
- force (gravity) is the only thing that can change the motion
Projectiles in Sports
experience linear motion
an object become projectile once it has been thrown, released, or hit (if air resistance is negligible)
the path of a projectile CANNOT be changed in flight if air resistance is negligible; typical parabolic
the path cannot be changed once projectile is airborne
initial position
angle of release
initial velocity
amount of force
vertical velocity
the projectile is constantly accelerating downward
horizontal velocity
the projectile will not slow down or speed ip (unless acted upon by an external force such as wind resistance)
In sports involving projectiles, the athlete’s objective usually concerns one of three things
- time of flight (how long)
- peak height reached by the projectile (how high)
- horizontal displacement (how far)
time of flight
depends on two things:
initial vertical velocity
initial vertical position
**the higher the initial height and the faster the initial upward velocity of the projectile, the longer it stays in the air
peak height
determined by two things:
initial height
initial vertical velocity
**higher the projectile is at release and the faster it is moving upward at the time of release, the higher it will go
maximizing horizontal displacement
determined by three things:
initial horizontal velocity
initial vertical velocity
initial height
**faster you throw something, the farther it will go
how to describe the motion of an object
position distance displacement speed velocity acceleration
what to consider when applying force to an object
mass weight relationship of mass and weight inertia relationship of mass and inertia
Law of Inertia
- objects do not want to move or change their motion unless acted upon by a net external force
- objects want to “maintain the current state of motion” that is, continue to move at the same speed and in the same direction (i.e. maintain constant velocity) whether in motion or at rest
Law of Acceleration
- if a net force acts on an object, it will accelerate in the direction the of the force, and its acceleration will be inversely proportionate to its mass
Law of Action/Reaction
- force/reaction force
- forces act in pairs - for every action, there is an equal and opposite reaction
Law of Gravitation
- basis for the force of gravity
Law of Universal Gravitation
- inspired by the fall of an apple on his family’s farm…
- law presented in two parts
1. All objects attract each other with a gravitational force that is inversely proportional to the square of the distance between the two parts
2. Force of gravity is proportional to the mass of each of the two bodies being attracted to each other
Mass
- all objects that have substance or matter have mass
- term “massive” indicates a body that takes up a large amount of space
- NFL lineman - plenty of muscle, bones, fat, tissue, fluids, and other substances in their bodies
- All objects with mass are attracted to other objects with mass
- Amount of gravitational attraction
- magnitude of mass
- distance apart
Weight
there is a gravitational attraction between the earth and your body
a more massive individual will exert a greater pull on the earth resulting in a higher reading on the scale
mass-weight relationship
- remember, the magnitude of the gravitational pull depends on the mass of the object and their distance apart
- spin of the earth causes equator to bulge
Inertia
resistance to action or to change
- the desire of an object to continue doing whatever it’s doing - even when it’s moving
- law of inertia - a body will remain at rest or continue to move at a constant velocity unless acted upon by an external force
- all objects want to remain motionless, but if a force moves them, then they want to continue moving in the same direction at a constant speed
mass-inertia relationship
- the more massive an object, the more it resists change
- examples
- takes more energy to start motion, and more energy to stop motion
- in athletics, inertia can work for you or against you depending on the situation
- in linear motion, mass is synonymous with inertia
- the more mass, the more inertia
Law of Universal Gravitation
F = G((m1-m2)/r2)) or F = mg
F = force of gravity G = universal constant of gravitation m1 = mass of an object m2 = mass of the earth r = radius of the earth
Gravity and Performance
changes in the acceleration of gravity due to latitude and altitude affect gravitational attraction
- higher distances will allow for greater velocities of movement
- objects continuously accelerate at constant rate all the way to the ground
- terminal velocity
