An athlete notices that, after lifting a 100 kilogram weight, he has to increase the weight to 105 kilograms before he feels that the weight is actually heavier. if the athlete later lifts a 200 kilogram weight, which of the following coincides with the just noticeable difference for this weight?
a. a 190 kg weight
b. a 205 kg weight
c. a 215 kg weight
d. a 220 kg weight

option A

Explanation:

given,

lifting weight = 100 Kg

increase in the weight = 105 Kg

later athlete lift = 200 Kg

Weber's law states that Just noticeable difference of weight is equal to ratio of change to the original.

Just noticeable difference for weight will be

    =

    = 5 %

since second weight is 200 Kg

so, Just noticeable difference of 200 Kg will be equal to ± 5 % of 200 Kg  which is equal to ± 10 Kg.

now,

Just noticeable difference for 200 Kg

     = 200 + 10 or 200 -10

     = 210 Kg or 190 Kg

Hence, the correct answer is option is option A

v=ir = 3x15 =45 v

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