In late 18th century, people wore rubber soled shoes called plimsolls, but they weren't the best sneakers. Around 1892, a US company named Keds started sneakers with a canvas top and rubber soles. By 1917, these were mass produced.
The magnetic fields are the reason why magnets repel and attract. eachother.
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The element Sodium (Na) has 11 protons and 1 valence electron.
Since its volume you do what it says 55 cm x 100 cm x 80cm and do 100 x 50 which is 5,000. then 5,000 x 80 which is 40,000. sorry i cant show work on here.