91Ó°ÊÓ

The force exerted by the particles within the system is known as the interaction force. This group accomplishes some tasks.

Write the work done by interaction forces as an expression.

$W_{\mathrm{int}}=-\mathrm{Δ}{U}_{\mathrm{imt}}……\left(1\right)$

Here, $W_{\text{int}}$is work done by interaction forces and $\mathrm{Δ}U$is the change in potential energy of the system.

Write the expression for work done by the external forces.

$W_{\mathrm{ett}}=\mathrm{Δ}{K}_{\mathrm{tot}}+\mathrm{Δ}{U}_{\text{imt}}…..\left(2\right)$

Here $W_{\mathrm{ea}}$is the work done by external forces and $\mathrm{Δ}{K}_{\text{tot}}$is the total change in kinetic energy of the system.

Calculate the amount of work done by the interaction force,

Substitute $-5J$for $∆U_{int}$in equation $\left(1\right)$.

$W_{int}=-(-5J)$

$=5J$

Hence, the work done by interaction force is $5J$.

Calculate the work done by external forces.

Substitute $7\mathrm{J}$for $\mathrm{Δ}{K}_{\text{tot}}$and $-5\mathrm{J}$for $\mathrm{Δ}{U}_{\text{int}}$in equation (2).

$W_{\mathrm{ext}}=7\mathrm{J}+(-5\mathrm{J})$

$=7\mathrm{J}-5\mathrm{J}$

$=2\mathrm{J}$

Hence, the work done by the interaction forces is $2\mathrm{J}$.