Physics - NLM Question with Solution | TestHub

The acceleration of the system of blocks is obviously $[60\mathrm{N}/(7+5+2+1)\mathrm{kg}]=4\mathrm{m}/{\mathrm{s}}^2$. Therefore, P exerts a force of $\left[(5+2+1)\mathrm{kg}\times 4\mathrm{m}/{\mathrm{s}}^2\right]=32\mathrm{N}$ whereas Q exerts a force of $[(2+1)\mathrm{kg}\times 4\mathrm{m}/$ ${\mathrm{s}}^2]=12\mathrm{N}$ on R. Similarly, R exerts a force of $\left[(1)\mathrm{kg}\times 4\mathrm{m}/{\mathrm{s}}^2\right]=4\mathrm{N}$ on S, so that a reaction force of same magnitude is exerted by S on R. Note that Q exerts a force of 32N on P and not 28 N as given in option(B). ]