1. Velocity Analysis
Lecture Notes
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

2. Velocity Analysis
Velocity analysis involves determining “how fast” certain
points on the links of a mechanisms are travelling.
Linear velocity of a point is the linear displacement of that
point per unit time.
Linear velocity is always perpendicular to a line that
connects the center of the link rotation to the point of
interest. Thus, linear velocity of a point in a link in pure
rotation is often called tangential velocity.
Rotational velocity of a link is the rotational (or angular)
displacement of that link per unit time.
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

3. Relationship Between Linear and Angular Velocity
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

4. Example 1:
The figure illustrates a cam mechanism used to drive the exhaust
port of an internal combustion engine. Point B is a point of interest
on the rocker plate. At this instant the cam forces point B upward
30 mm/s. Determine the rotational velocity of the rocker plate, in
rpm and the velocity of point C, in mm/sec.
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

5. Solution:
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

6. Relative Velocity
The difference between motion of two points
is termed relative motion.
Relative velocity is a term used when the
velocity of the object is related to that of
another reference object, which can also be
moving.
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

7. Relative Velocity
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

8. Example 2:
The figure below illustrates a cargo lift mechanism for a delivery
truck. At this instant, point A has a velocity of 12 in/s in the
direction shown, and point B has a velocity of 20 in/s, also in the
direction shown. Determine the rotational velocity of the lower
link, in rpm and the relative velocity of point B relative to point A.
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

9. Analytical Solution
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

10. Graphical Solution
Using CAD software:
Reference: Machines and
Mechanisms Applied
Kinematics by David H. Myszka

11. Reference:
Machines and Mechanisms Applied Kinematic
Analysis by David H. Myszka. © 1999 by
Prentice-Hall, Inc. Page 137 - 144.