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Find mass of an object hanging on string

  • Thread starter angi-18
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  • #1
9
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please tell me how to find the mass of an object which is hang on the string???
I mean what would be the formula ????
i am also writing here my numerical question....
Q:two bodies A and B are attached to a string which passes over a pulley so that two bodies hang vertically.if the mass of body A is 4.8 kg find the mass of body B which moves down with an acceleration of 0.2m/s.s.(g=9.8m/s.s)
 

Answers and Replies

  • #2
993
13
Make a diagram of the situation.

Look carefully at mass B. How many forces act on mass B?
 
  • #3
9
0
no force is acting on mass B the formula given in our text book is:
α=(mB-mA/mB+mA) x g

i dont know how to arrange it to find the mass B......:confused:
 
  • #4
993
13
We are trying to show HOW to get that formula.

Look at mass B. It has the Earth pulling it down - that is the weight mB x g of mass b - and the string pulling it up by a tension T.

Now use Fnet = ma for mass B.
 
  • #5
993
13
Fnet = ma ............for mass B

mBg - T = mBa

Fnet = ma .............for mass A

T - mAg = mAa

If the tension T is eliminated from the above two equations then one gets the equation required.
 

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