Question

two objects 5kg and 7kg are attached to the ends of an inextensible which passess over a frictionless pulley such that 5 kg is moving over a frictionless horizontal surface and the mass 7 kg is moving vertically downwards. find the acceleration in the system and tension in the string​

Answer 1

Points to note before solving:

• Draw the figure as per mentioned in the question.

Now, as per figure in attached image,we can say that:

• Single string is present,so tension will be same throughout.
• Both objects are moving together as system so acceleration will be same for both.

Solution:

$\rm F_{net} = F_{driving}- F_{opposing} = ma$

For 5 kg

• T = 5a ------(1)

For 7 kg

• 7g - T = 7a
• 7g - 5a = 7a -----(by eq. 1)
• 7g = 12a

$\implies \rm a = \dfrac{7g}{12}$

Putting "a" in eq 1.

• T = 5a = 5(7g/12)

$\implies \rm T = \dfrac{35g}{12}$

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