005a velocity analysis

Velocity Analysis Lecture NotesReference: Machines andMechanisms AppliedKinematics by David H. Myszka

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 andMechanisms AppliedKinematics by David H. Myszka

Relationship Between Linear and Angular VelocityReference: Machines andMechanisms AppliedKinematics by David H. Myszka

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 andMechanisms AppliedKinematics by David H. Myszka

Solution:Reference: Machines andMechanisms AppliedKinematics by David H. Myszka

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 andMechanisms AppliedKinematics by David H. Myszka

Relative VelocityReference: Machines andMechanisms AppliedKinematics by David H. Myszka

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 andMechanisms AppliedKinematics by David H. Myszka

Analytical SolutionReference: Machines andMechanisms AppliedKinematics by David H. Myszka

Graphical SolutionUsing CAD software: Reference: Machines and Mechanisms Applied Kinematics by David H. Myszka

005a velocity analysis

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