Answer to Question #276341 in Mechanical Engineering for Karthick

Question

In a pin jointed four bar mechanism ABCD, the lengths of various links are as follows:

AB= 25 mm; BC = 87.5 mm : CD=50 mm and AD = 80 mm. The link AD is fixed and the angle BAD = 135. If the velocity of B is 1.8 m/s in the clockwise direction, find 1. velocity and acceleration of the mid point of BC. and 2. angular velocity and

angular acceleration of link CB and CD.

Answer 1

Kinematic link

In a machine each part which moves relative to other part that is known as kinematic link.

Link may contain several parts which are rigidly fastened together.

 

Types of links 

1. Rigid link : A link which does not undergo any deformation while transmitting motion.
2. Flexible link : A flexible link is one which is partly deformed in a manner not to affect the transmission of motion.

 

Kinematic pair

The two links of machine are in contact with each other are said to form a pair. If the relative motion between them is completely or successfully constrained the pair is known as kinematic pair.

We solve this problem using

 

The velocity of link AB is given by,

  

Lets find velocity of remaining links for that follow following steps,

Draw space diagram using given information with suitable scale,

Scale: 1cm = 20m/s

 

Now we will draw velocity diagram,

A and D are fixed points so we will take it as 1 point.

Now from point ad draw vector of velocity of B perpendicular to link AB at suitable scale

Scale: 1cm = 0.1m/s

V_B = 0.4725m/s

ab = 4cm