A movable pulley has its support point moving upward at 10 m s⁻¹. One end of the string is fixed at B and block A is attached to the other end. The velocity of A is:

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G1 Physics · Accepted Answer

For a single movable pulley, two string segments change with pulley motion. String constraint gives vₐ=2pulley speed=20 m s⁻¹ in the direction required to keep total length constant. Option C.