Question

Figure shows a man of mass 50kg standing standing on a light weighing machine

Answer 1

Given:

Figure shows a man of mass 50kg standing on a light weighing machine kept in a box of mass 30kg. The box is hanging from a fixed pulley to the ceilling through a massless rope, the other end of which is held by the man. The man manages to keep the box at rest.

To find:

Reading shown by weighing machine.

Calculation:

Let mass of man be M and mass of lift be m;

According to FBD of man:

$\rm{T + N = Mg } \: \: \: \: ......(1)$

According to FBD of lift:

$\rm{T = mg + N } \: \: \: \: \: \: ......(2)$

Putting value of T in eq.(1):

$\therefore \: \rm{T + N = Mg }$

$= > \: \rm{mg + N + N = Mg }$

$= > \: \rm{mg + 2N = Mg }$

$= > \: \rm{ 2N = (M - m)g }$

$= > \: \rm{ N = \dfrac{(M - m)g}{2} }$

$= > \: \rm{ N = \dfrac{(50 - 30) \times 10}{2} }$

$= > \: \rm{ N = \dfrac{(20) \times 10}{2} }$

$= > \: \rm{ N = 100 \: Newton }$

So,final answer is:

$\boxed{\bf{ weight \: shown = N = 100 \: Newton } }$