Determine the speed with which block B rises in fig. if the end of the cord at A is pulled down with a speed of `2ms^(-1)`.

Explanation

Speed of C and B will be same as shown. Let it be v.
`|x_(B)|=|x_(C)|`
Using constraint for string passing over C:
`(x_(a)-x_(C))+(x_(C)-x_(B))(-x_(B))=0`
`x_(A)-2x_(C)-2x_(B)=0`
But `x_(B)=x_(C)implies x_(A)-4x_(B)=0`
or `v_(A)=4v_(B)`
Hence, `v_(B)=(v_A)/(4)=2/4 = 0.5 ms^(-1)`.