# Problem: A system of two objects has ΔKtot = 7 J and ΔUint = -3 J.Part AHow much work is done by interaction forces?Part BHow much work is done by external forces?

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###### FREE Expert Solution

Work and energy theorem:

$\overline{){\mathbf{W}}{\mathbf{=}}{\mathbf{-}}{\mathbf{∆}}{\mathbf{U}}}$

From the conservation of energy principle:

$\overline{){\mathbf{W}}{\mathbf{=}}{\mathbf{∆}}{\mathbf{K}}{\mathbf{+}}{\mathbf{∆}}{\mathbf{U}}}$

###### Problem Details

A system of two objects has ΔKtot = 7 J and ΔUint = -3 J.

Part A

How much work is done by interaction forces?

Part B

How much work is done by external forces?