Two masses m1 = 5kg and m2 = 4.8 kg  tied to a string are hanging over a light frictionless pulley. What is the acceleration of the masses when lift free to move?

( g = 9.8 m/s2 )

 

  • Option 1)

    0.2 m/s2

  • Option 2)

    9.8 m/s2

  • Option 3)

    5  m/s2

  • Option 4)

    4.8 m/s2

 

Answers (1)

As we learnt in

Motion of connected blocks over pulley -

Equation of motion for   m_{1}

F_{net}=T-m_{1}g=m_{1}a

Equation of Motion for   m_{2}

F_{net}=m_{2}g-T=m_{2}a

 

- wherein

a=\frac{[m_{2}-m_{1}\:]g}{m_{1}+m_{2}}

T=\frac{2m_{1}m_{2}\:g}{m_{1}+m_{2}}


 

 

 \frac{a}{g}= \frac{(m_{1}-m_{2})}{(m_{1}+m_{2})}= \frac{\left ( 5-4.8 \right )}{\left ( 5+4.8 \right )}= \frac{0.2}{9.8}

or\: \: \: a= g\times \frac{0.2}{9.8}= \frac{9.8\times 0.2}{9.8}= 0.2 ms^{-2}

Correct option is 1.


Option 1)

0.2 m/s2

This is the correct option.

Option 2)

9.8 m/s2

This is an incorrect option.

Option 3)

5  m/s2

This is an incorrect option.

Option 4)

4.8 m/s2

This is an incorrect option.

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