Question

Three frictionless trolleys are being pulled by a toy engine. The trailing trolley has mass $3kg$. The middle trolley has mass $2kg$. The leading trolley has mass $1kg$.
If the pulling force is $F=6N$, how much tension $T$ exists in the portion connecting the $3kg$ and the $2kg$ trolleys?

• A. $0N$
• B. $1N$
• C. $2N$
• D. $3N$
• E. $6N$

Answer 1

Answer: (D)

$3N$

Given : $F=6$ N $m_1=1$ kg $m_2=2$ kg $m_3=3kg$

Let the tension in the string between $3kg$ and $2kg$ be $T$ and the acceleration of the whole system be $a$.

Mass of whole system $M=1+2+3=6$ kg

Thus acceleration of whole system $a=\frac{F}{M}=\frac{6}{6}=1$ $m/s^2$

For block of mass $3kg$ : $T=m_{3}a$

$\therefore$ $T=3\times 1=3$ N