MCQ
Figure shows three blocks in contact and kept on a smooth horizontal surface. What is ratio of force exerted by block $A$ on $B$ to that of $B$ on $C$
- A$2 : 1$
- ✓$3 : 1$
- C$6 : 1$
- D$1 : 2$
✓
Answer
Correct option: B.
$3 : 1$
b
Total mass of three blocks: $M=5+2+1=8 k g$
Total mass of three blocks: $M=5+2+1=8 k g$
Acceleration of the blocks: $a=\frac{F}{M}=\frac{16}{8}=2$
Let $N_{A B}$ and $N_{B C}$ be the force exerted by block $A$ on $B$ and by block $B$ on $\mathrm{C}$ respectively.
$F-N_{B A}=m_{A} a$ where $N_{A B}=N_{B A}$
$\therefore 16-N_{B A}=5 \times 2=10$
$\Rightarrow N_{B A}=6=N_{A B}$
$N_{A B}-N_{C B}=m_{B} \times a=2 \times 2=4$
$\therefore N_{C B}=N_{B C}=6-4=2$
$\therefore \frac{N_{A B}}{N_{B C}}=\frac{6}{2}=\frac{3}{1}$
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