Question

Determine the speed with which block $B$ rises in figure if the end of the cord at $A$ is pulled down with a speed of $2m/s$.

• A. $0.5m/s\uparrow$
• B. $0.3m/s\uparrow$
• C. $0.9m/s\uparrow$
• D. $0.6m/s\uparrow$

Answer 1

The correct option is A $0.5m/s\uparrow$

$v_A=$ speed of block A

$v_B=$ speed of block B

From constrain equation

$v_A+2v_B-2v_C=0$.....(1)

$v_B+v_C=0\Rightarrow v_C=-v_B$

$\Rightarrow v_B=-\frac{1}{4}{v}_A$

$=-\frac{2}{4}=-0.5$

speed with which block B rises is $0.5m/s$