# Lecture 10 - Torque and Rotation Flashcards

1

Q

what is torque?

A

- moment of force
- force must be applied at the center of mass (for acceleration)
- newtons second law but with rotation

2

Q

what happens if the force is not pushed at the center of mass?

A

- the body rotates
- angular acceleration occurs alongside regular acceleration (around the center of mass)
- almost always these two occur together

3

Q

how do you calculate torque?

A

- force x perpendicular distance from the center of mass = torque
- aka T = F x D+
- the distance is called the lever arm/ moment arm

4

Q

what is a lever arm?

A

- the distance between the point of application on the line of action and the joint

5

Q

how do you calculate angular acceleration?

A

- T = I x alpha
- where I is moment of inertia (rotational mass aka rotational resisitance)
- where alpha = angular acceleration

6

Q

what is linear mass?

A

- the resistance the body has to being accelerated

7

Q

what are the 4 characteristics of a vector? How do they relate to torque?

A

- magnitude –> T = F x d+
- direction –> along the axis of rotation (right-hand rule)
- point of application –> center of the joint
- line of action –> along the axis of rotation

8

Q

what is the right hand rule?

A

- torque vector is the direction of the thumb if your fingers curve in the direction of rotation
- thumb acts as the axis of rotation

9

Q

what is torque if there is no lever arm?

A

- torque is zero
- torque cannot exist if there is no lever arm
- T = F x 0 –> T = 0

10

Q

how does torque relate to the center of mass?

A

- overall center of mass = where all torque created are at balance in the body

11

Q

what happens if torques are balanced?

A

- no rotation occurs

12

Q

why are pushups on your knees easier?

A

- shortening the distance from axis of rotation
- if d+ is smaller, torque is smaller (T = F x d+)
- if torque is smaller, force is smaller –> therefore it is easier