levers - lesson 8 & 9 Flashcards
define a lever
a rigid bar pivoted on a fixed point and used to transmit force
what are the three main parts of levers?
Weight or resistance to be moved
Axis or pivot point = fulcrum.
Application of force to move the weight or resistance
what is the fulcrum?
the point around which the lever rotates
what is the force arm?
the distance between the fulcrum and the point at which the force is applied.
what is the resistance arm?
the distance between the fulcrum and the center of the resistance
what is the Input (Effort) Force?
Force exerted ON the lever
what is the Output (Resistance) Force?
Force exerted BY the lever
what are the functions of levers?
Increase the application of force
Increase the speed of movement
how is the application of force increased?
by making the FORCE ARM longer than the RESISTANCE ARM. by moving the axis on a 1st class lever to increase the size of the force arm or creating a 2nd class lever that naturally has a longer force arm
how is the speed of movement increased?
making the RESISTANCE ARM longer than the FORCE ARM = allows the force to move the resistance through a greater range of motion. by moving the axis on a 1st class lever to increase the size of the resistance arm or creating a 3rd class lever that naturally has a longer resistance arm
what is the linear velocity of a rotating object?
the product of the object’s angular velocity and its radius rotation
= angular velocity x radius of rotation
how do athletes maximize the linear velocity of release/contact?
by fully extending their arms (throwing/striking) or legs (kicking) at the point of contact
how does using a bat affect linear velocity?
- extension to the arm lever system
- generating greater linear velocity at impact due to the increase of radius rotation that the implement provides
what is a 1st class lever?
the axis/fulcrum is located in the middle with the force and resistance on either side.
FAR
what is a 2nd class lever?
the axis/fulcrum is located at the end with the resistance in the middle and force applied at the opposite end
ARF
why does a 2nd class lever have an advantage?
due to always having a longer force arm than the resistance arm, therefore producing high forces
what are 3rd class levers?
axis/fulcrum is located at one end with the application of the force in the middle and resistance applied at the opposite end
- they always have a longer resistance arm
RFA
what is the most common lever in the human body and why?
- built for speed
- large resistance arm ensures ↑ speed can be obtained
describe a 3rd class lever in the human body
muscle attachment represents the application of force, the joint represents the axis/fulcrum and the weight/load represents the resistance
describe a 3rd class lever in regards to striking
By increasing the length of the resistance arm, it is possible to generate greater velocity / angular momentum of the bat
= greater momentum being transferred onto the ball.
what is a negative of increasing the length of a lever in striking?
results in an increased moment of inertia (resistance to rotation) which may negatively affect control and/or angular velocity generated.
what are the 3 factors affecting the use of levers?
length of lever
inertia of lever
amount of force produced by the athlete
how does the length of the lever affect its use?
- Velocity is greatest at the distal end of a lever
- Longer the lever, the greater the velocity at impact
- longer bat length creates higher velocity and momentum at impact provided the athlete can control the longer lever – longer generally means more moment of inertia (resistance to rotation)
how does the inertia of the lever affect its use?
- The longer the lever, the greater the moment of inertia, and therefore the more difficult it is to rotate
- By choking down the bat in striking sports, athletes can reduce the rotational inertia of the implement, therefore, making it easier to swing
