Question

two masses A and B measuring 3 kg and 4 kg are connected by a massless and inextensible string. if a force of 20 N is applied to 7 kg the tension in the string is

Answer 1

$\underline{ \boxed{ \bold{ \huge{ \purple{Answer}}}}} \\ \\ \star \rm \: \red{Given} \\ \\ \implies \rm \: Two \: masses \: A \: and \: B \: of \: mass \: 3 \: kg \: and \: 7 \: kg \\ \rm \: are \: connected \: by \: massless \: and \: inextensible \\ \rm \: string. \\ \\ \implies \rm \: A \: force \: of \: 20\:N \: applied \: on \: 7 \: kg \: mass. \\ \\ \star \rm \: \red{To \: Find} \\ \\ \implies \rm \: tension \: in \: string \\ \\ \star \rm \: \red{Formula} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \boxed{ \pink{ \rm{F \tiny{net}} = (m{ \tiny{1}} + m{ \tiny{2}})a}}\\ \\ \implies \rm \: net \: force \: on \: 7 \: kg \: mass \: block \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \boxed{ \rm{ \pink{F{ \tiny{7 \: kg}} = 7a = F{ \tiny{net}} - T}}} \\ \\ \star \rm \: \red{Calculation} \\ \\ \implies \rm \: F{ \tiny{net}} = 20 = (7 + 3)a \\ \\ \implies \: \boxed{ \rm{a = 2 \: \frac{m}{ {s}^{2} }}} \\ \\ \implies \rm \: 7a = 20 - T \\ \\ \implies \rm \: T = 20 - 14 = 6 \: N \\ \\ \huge{\blue{ \star}} \: \boxed{ \orange{ \huge{ \rm{T = 6 \: N}}}} \: \huge{ \blue{ \star}}$