Question

The two links OA and OB are connected by a pin joint at O. If the link OA turns with angular velocity ω1 rad/s in the clockwise direction and the link OB turns with angular velocity ω2 rad/s in the anti-clockwise direction, then the rubbing velocity at the pin joint O is

(a) ω1.ω2.r

(b) (ω1-ω2)r

(c) (ω1+ω2)r

(d) (ω1-ω2)2r

I had been asked this question in an online quiz.

This interesting question is from Linear Velocity in portion Kinematics & Kinetics of Motion of Machine Kinematics

Answer 1

Right answer is (c) (ω1+ω2)r

Explanation: Consider two links OA and OB connected by a pin joint at O

Let ω1 = Angular velocity of the link OA or the angular velocity of the point A with respect to O.

ω2 = Angular velocity of the link OB or the angular velocity of the point B with respect to O, and

r = Radius of the pin.

According to the definition,

Rubbing velocity at the pin joint O

= (ω1 – ω2) r, if the links move in the same direction

= (ω1 + ω2) r, if the links move in the opposite direc