Exam 1 - Projectiles in Sport & Linear Kinematics 2

Question 1

Projectiles

Answer 1

anything in motion and airborne

• force (gravity) is the only thing that can change the motion

Question 2

Projectiles in Sports

Answer 2

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

Question 3

initial position

Answer 3

angle of release

Question 4

initial velocity

Answer 4

amount of force

Question 5

vertical velocity

Answer 5

the projectile is constantly accelerating downward

Question 6

horizontal velocity

Answer 6

the projectile will not slow down or speed ip (unless acted upon by an external force such as wind resistance)

Question 7

In sports involving projectiles, the athlete’s objective usually concerns one of three things

Answer 7

• time of flight (how long)
• peak height reached by the projectile (how high)
• horizontal displacement (how far)

Question 8

time of flight

Answer 8

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

Question 9

peak height

Answer 9

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

Question 10

maximizing horizontal displacement

Answer 10

determined by three things:

initial horizontal velocity
initial vertical velocity
initial height

**faster you throw something, the farther it will go

Question 11

how to describe the motion of an object

Answer 11

position 
distance
displacement 
speed 
velocity 
acceleration

Question 12

what to consider when applying force to an object

Answer 12

mass
weight
relationship of mass and weight 
inertia 
relationship of mass and inertia

Question 13

Law of Inertia

Answer 13

• 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

Question 14

Law of Acceleration

Answer 14

• 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

Question 15

Law of Action/Reaction

Answer 15

• force/reaction force

- forces act in pairs - for every action, there is an equal and opposite reaction

Question 16

Law of Gravitation

Answer 16

• basis for the force of gravity

Question 17

Law of Universal Gravitation

Answer 17

• 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

Question 18

Mass

Answer 18

• 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

Question 19

Weight

Answer 19

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

Question 20

mass-weight relationship

Answer 20

• 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

Question 21

Inertia

Answer 21

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

Question 22

mass-inertia relationship

Answer 22

• 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

Question 23

Law of Universal Gravitation

Answer 23

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

Question 24

Gravity and Performance

Answer 24

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