文档介绍：理论力学 Theoretical Mechanics
运动学第六章刚体的基本运动
力学教研室
Planar Basic Kinematics of
Rigid bodies
Planar Basic Kinematics of Rigid Bodies
Motion of Rigid Bodies
Motion of rigid bodies
Translation (平移)
Fixed-axis Rotation (定轴转动)
Planar motion (平面运动)
Common motion (一般运动)
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Translation is the special case in which the body moves without rotation, that is, any line in the body remains parallel to its initial position.
例子1
例子2
Definition
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Characteristics
Velocity and acceleration
Because BA is a constant vector, we obtain:
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Characteristics
Because Point A and B are arbitrary chosen, we can draw the conclusion as follows:
Each point on the rigid body will produce the same path after the rigid body translates, and at the same time, the velocities and accelerations of each point are the same.
We can regard the translation of rigid body as a particle’s motion
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Sample Problem
Compute the velocity and acceleration of the middle point M when t=0s and t=2s
运动
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Sample Problem
[Solution]
The block moves translation
Setup the curvilinear coordinates as the figure shown.
Planar Basic Kinematics of Rigid Bodies
PART A Translation
Part A-translation
Sample Problem
When t=2s, the results can be found in Chinese textbook page 134, here omitted.
Planar Basic Kinematics of Rigid Bodies
PART B Rotation about a Fixed Axis
Part B-Rotation
When the body moves, one line on the body keeps its initial position, this kind of motion can be said to rotation about a fixed axis.
例子
Definition
Planar Basic Kinematics of Rigid Bodies
PART B Rotation about a Fixed Axis
Part B-Rotation