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Mechanical Properties Of Fluids

Question
CBSEENPH11020201

A spring balance has a scale that reads from 0 to 50 kg. The length of the scale is 20 cm. A body suspended from this balance, when displaced and released, oscillates with a period of 0.6 s. What is the weight of the body?

Solution
Maximum mass that the scale can read, M = 50 kg 
Maximum displacement of the spring = Length of the scale, = 20 cm = 0.2 m 
Time period, T = 0.6 s 
Maximum force exerted on the spring, F = Mg 

where, 
g = acceleration due to gravity = 9.8 m/s

= 50 × 9.8 = 490 
∴  Spring constant, k = straight F over straight l space equals space fraction numerator 490 over denominator 0.2 end fraction space equals space 2450 space N divided by m
Mass m, is suspended from the balance. 
Time space period comma space straight T space equals space 2 straight pi space square root of straight m over straight K end root space

therefore space space space space space space space space space space space space space space space space space space straight m space equals space open parentheses fraction numerator straight T over denominator 2 straight pi end fraction close parentheses squared space straight x space straight k space space

space space space space space space space space space space space space space space space space space space space space space space space space equals space open parentheses fraction numerator 0.6 over denominator 2 space straight x space 3.14 end fraction close parentheses squared space straight x space 2450 space

space space space space space space space space space space space space space space space space space space space space space space space space equals space 22.36 space kg
 
∴Weight of the body = mg 
                               = 22.36 × 9.8
                                = 219.167 N 
Hence, the weight of the body is about 219 N.