m = 500g = 0,5 kg
p = 1kPa = 1000 Pa
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l = ?
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P = G/S => S = G/P
G = m·g = 0,5kg·9,8N/kg = 4,9 N } =>
=> S = 4,9N/1000Pa = 4,9N/1000N/m² = 0,0049 m² = 49 cm²
S = 49 cm² = l² =>
=> l = √49 = 7 cm