levers - lesson 8 & 9

Question 1

define a lever

Answer 1

a rigid bar pivoted on a fixed point and used to transmit force

Question 2

what are the three main parts of levers?

Answer 2

Weight or resistance to be moved
Axis or pivot point = fulcrum.
Application of force to move the weight or resistance

Question 3

what is the fulcrum?

Answer 3

the point around which the lever rotates

Question 4

what is the force arm?

Answer 4

the distance between the fulcrum and the point at which the force is applied.

Question 5

what is the resistance arm?

Answer 5

the distance between the fulcrum and the center of the resistance

Question 6

what is the Input (Effort) Force?

Answer 6

Force exerted ON the lever

Question 7

what is the Output (Resistance) Force?

Answer 7

Force exerted BY the lever

Question 8

what are the functions of levers?

Answer 8

Increase the application of force

Increase the speed of movement

Question 9

how is the application of force increased?

Answer 9

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

Question 10

how is the speed of movement increased?

Answer 10

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

Question 11

what is the linear velocity of a rotating object?

Answer 11

the product of the object’s angular velocity and its radius rotation
= angular velocity x radius of rotation

Question 12

how do athletes maximize the linear velocity of release/contact?

Answer 12

by fully extending their arms (throwing/striking) or legs (kicking) at the point of contact

Question 13

how does using a bat affect linear velocity?

Answer 13

• extension to the arm lever system

- generating greater linear velocity at impact due to the increase of radius rotation that the implement provides

Question 14

what is a 1st class lever?

Answer 14

the axis/fulcrum is located in the middle with the force and resistance on either side.
FAR

Question 15

what is a 2nd class lever?

Answer 15

the axis/fulcrum is located at the end with the resistance in the middle and force applied at the opposite end
ARF

Question 16

why does a 2nd class lever have an advantage?

Answer 16

due to always having a longer force arm than the resistance arm, therefore producing high forces

Question 17

what are 3rd class levers?

Answer 17

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

Question 18

what is the most common lever in the human body and why?

Answer 18

• built for speed

- large resistance arm ensures ↑ speed can be obtained

Question 19

describe a 3rd class lever in the human body

Answer 19

muscle attachment represents the application of force, the joint represents the axis/fulcrum and the weight/load represents the resistance

Question 20

describe a 3rd class lever in regards to striking

Answer 20

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.

Question 21

what is a negative of increasing the length of a lever in striking?

Answer 21

results in an increased moment of inertia (resistance to rotation) which may negatively affect control and/or angular velocity generated.

Question 22

what are the 3 factors affecting the use of levers?

Answer 22

length of lever
inertia of lever
amount of force produced by the athlete

Question 23

how does the length of the lever affect its use?

Answer 23

• 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)

Question 24

how does the inertia of the lever affect its use?

Answer 24

• 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

Question 25

how does the amount of force produced by the athlete affect its use?

Answer 25

• The amount of force an athlete is able to generate via their muscles determines the length of the lever the athlete should use
• Longer levers are usually heavier therefore more force is required to move them