Important Short Questions and Answers: Kinematics Of Linkage Mechanisms

1.  What are the components of acceleration?

Radial component of acceleration

Tangential component of acceleration

2.  Write an expression for find number of instantaneous centers in a         mechanism.

N=n(n-1)/2,         n-no of links

3. What is expression for Coriolis componenet of acceleration?

                         a BC

=2rw  

Where w=Angular velocity of

‘OA’ V=Linear velocity of ‘B’

4.     How can we represent the direction of linear velocity of any point on a link with respect to another point on the same link?

The direction of linear velocity of any point on a link with respect to another point on the

same link the direction is perpendicular to the line joining the points.

5.     What is the expression for radial and tangential component of acceleration?

Radial component

Arc

OB=wOB*OB Tangential component

Arc OB=aOB*OB

Where wOB=Angular velocity of link OB aOB=Angular acceleration of link OB OB=Length of link OB.

(Radial component of acceleration is perpendicular to the velocity of the component and

tangential component is perpendicular to link position)

6.  Define instantaneous center and instantaneous axis?

Instantaneous center of a moving body may be defined as that center which goes on changing from one instant to another.

Instantaneous axis is a line drawn through an instantaneous center and perpendicular to the plane of motion.

7.     What are the names of instantaneous center?

Virtual center Centro Rotopole.

8.     How can we apply instantaneous center method to determine velocity?

Consider three points A, B, C on a rigid link. I am being instantaneous Center. Let VA,

VB, VC be the points A, B & C. Then we have

VA/IA=VB/IB=VC/IC

9.  What is the objective of Kinematic analysis?

The objective of Kinematic analysis is to determine the Kinematic quantities such as displacement, velocity and acceleration of the element in a mechanism.

10. Write any two rules to locate Instantaneous center.

When two links are connected by a pin joint the instantaneous center lies on the center of

the pin.

When two links have a sliding contact, the instantaneous center lies at infinity in a direction perpendicular to the path of motion of slide.

11. Define Kennedy’s theorem.

The Kennedy’s theorem states that if three bodies move relatively to each other, they

have three instantaneous centers and lie on a straight line.

12. What is meant by efficiency of a mechanism?

Efficiency of a mechanism is defined as the ratio of the product of force and velocity in

driven link to the product of force and velocity in driving link.

13. A pin joins two links A & B. A rotates with wA angular velocity and B rotates with

wB angular velocity in opposite direction. What is the rubbing velocity of that point?

Rubbing velocity of pin = ( wA + wB ) * r Where ‘r’ is the radius of pin.

14. What is the magnitude of linear velocity of a point B on a link AB relative to A?

The magnitude of linear velocity of a point B on a link AB, which rotates with

‘w’ angular velocity with respect to A is: VB/A =w A/B *AB