angular kinetics - lesson 5

Question 1

what are the two types of forces?

Answer 1

concentric force

eccentric force

Question 2

describe concentric force

Answer 2

a force applied to produce linear motion

• hitting a floating serve in volleyball
• the ball doesn’t rotate while it travels on a linear path

Question 3

describe eccentric force

Answer 3

an off-center force applied to produce angular motion

• motion of a body about a fixed point or axis
• hitting a top spin serve in volleyball
• ball rotates while it travels on a linear path

Question 4

what is angular rotation?

Answer 4

movement of a body around an axis or spinning

Question 5

what causes angular rotation?

Answer 5

an eccentric force

Question 6

how can angular rotation be increased?

Answer 6

• increase the amount of force applied

- increase the distance from the axis of rotation to where the force is applied

Question 7

what are force couples?

Answer 7

When two equal, but oppositely directed forces act on opposite sides of an axis of rotation
- causes the forces that produce linear motion to cancel each other out, causing the object to rotate in a fixed position

Question 8

what happens with a smaller moment arm?

Answer 8

less angular rotation is achieved when the same amount of force is applied

Question 9

what happens with a larger moment arm?

Answer 9

means more angular rotation is achieved when the same amount of force is applied

Question 10

what is a moment arm?

Answer 10

distance from the application of force to axis of rotation

Question 11

define torque

Answer 11

the turning effect created as a result of an eccentric force being applied around a pivot or axis.

Question 12

what is the formula for torque?

Answer 12

Torque = Force x Distance

Question 13

how does the momentum arm length affect torque?

Answer 13

smaller moment arm = small torque created

Question 14

how can torque be increased?

Answer 14

by applying greater force

increasing the length of the moment arm

Question 15

how can torque be decreased?

Answer 15

applying less force

decreasing the length of the moment arm

Question 16

what factors influence the amount of torque placed on a ball?

Answer 16

• Amount of force applied (product of muscular contraction and athlete’s lever length)
• Length of moment arm – longer moment arm (force applied further away from the center of the ball) produces increased torque