Question

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

Answer 1

Given:

v=2m/s
we then write the equation for the total length of the cord
Sa(t)-sc(t) +sb)t-sc(t)+sb(t)=constant
sc(t)+sb(t)=constant
When we take derivatives of  cord equations:
d/dt(sa-sc+sb-sc+sb)=0
d/dt(sc+sb)=0
we get
va+2vb-2vc=0-----(1)
and
vb+vc=0-----(2)
solve the second of the two equations for velocities: to eliminate Vc
va+2vb-2vc=0
and
vb+vc=0
we get
vc=-vb

substituting this equation in equation we getvb=-1/4Va=- 2/4=-1/2 m/s

∴ vb=-0.5m/s

Answer 2

Explanation:

Anwer is 0.5 m/s this Anwer is explained above in picture