Two blocks are connected by a very light string passing over amassless and frict

Question

Two blocks are connected by a very light string passing over amassless and frictionless pulley (see figure). Traveling atconstant speed, the 18.5-N blockmoves104.5 cm to the right andthe 12.8-N blockmoves 104.5 cm downward.(Let w1 = 18.5 Nand w2 = 12.8 N.)

During this process, how much work is done onthe 12.8-N block bygravity?


During this process, how much work is done on the 12.8-N block by the tension in the string?


(b) During this process, how much work is done onthe 18.5-N block bygravity?


During this process, how much work is done on the 18.5-N block by the tension in the string?


During this process, how much work is done on the 18.5-N block by friction?

During this process, how much work is done on the 18.5-N block by the normal force?

During this process, how much work is done onthe 12.8-N block bygravity?


During this process, how much work is done on the 12.8-N block by the tension in the string?


(b) During this process, how much work is done onthe 18.5-N block bygravity?


During this process, how much work is done on the 18.5-N block by the tension in the string?


During this process, how much work is done on the 18.5-N block by friction?

During this process, how much work is done on the 18.5-N block by the normal force?

Explanation / Answer

During this process, how much work is done onthe 12.8-N block bygravity?
Agravity=mgh  = 12.8 x 1.045 =13.376J

During this process, how much work is done on the 12.8-N block by the tension in the string?
Sincethey are moving at constant speed, the total work done by externalforce must be zero, hence
Astring=-Agravity=-13.376J

(b) During this process, how much work is done onthe 18.5-N block bygravity?
Thisone move right only, the work done by gravity is zero

During this process, how much work is done on the 18.5-N block by the tension in the string?
Thetension of the string exert on 18.5N-block equal to 12.8N-block.They move the same distance so the work done on them must have thesame magnitude. But tension force exert on 18.5N-block is in thedirection of movement, so the work done by it is positive and equalto 13.376J

During this process, how much work is done on the 18.5-N block by friction?
Since they are moving at constant speed, thetotal work done by external force must be zero, hence
Afriction=-Astring=-13.376J
During this process, how much work is done on the 18.5-N block by the normal force? the normal force is always perpendicular tothe movement, so the work done by it is always zero

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