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
