Question

In the planar mechanism shown in figure the link lengths are given in cm. The ternary link DCE is parallel to the input crank AB. The links BC and EF are parallel to each other at the instant. The slider F is guided in the vertical direction. If the crank AB has an angular velocity of 6 rad/sec, the velocity of the slider is

• A. 0.3 m/s downwards
• B. 1.8 m/s upwards
• C. 1.8 m/s downwards
• D. zero

Answer 1

The correct option is C 1.8 m/s downwards

Number of likes = 6,

$BC||EF$ and $AB||DE$

$(V_6=V,{\omega }_{AB}=6rad/sec)$

$\Rightarrow$ Because DE||AB thus link BC translates.

$(\because {\omega }_{BC}=0)$


velocity of point $B=V_B=\omega r$

$=6\times 20=120cm/sdownwards$

${\overline{V}}_C={\overline{V}}_B=120cm/s$

thus ${\omega }_4\times 40=120$

${\omega }_4=\frac{120}{40}=3rad/sec$

now, BC||EF link EF also translates

$(V_E=V_F)$

$\therefore V_E=3\times \frac{60}{100}=1.8m/sdownwards$