A generation is about one third of a lifetime. Approximately how many generations have passed since the beginning of recorded history? Half the life expectancy of a human is of the order of 10^9 s

The answer is  the potential energy of the bob at position b is 1.47 joules.if the maximum height of the bob is 0.45 meters when it swings back,1.323   joules of energy was transformed to thermal energy.hope this

Ithink the answer for this is: an electromagnet is a magnet  with a soft metal core.