If a cell is like a school, then the nucleus would be .

The density of a substance is 4.0 g/cm3. if a sample of the substance has a volume of 25 cm3 then what is the mass

Aball of mass 0.3kg is released from rest at a height of 8m.how fast is it going when it hits the ground? accleration due to gravity is g=9.8m/s

The radioactive isotope of lead, pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.3 hours. if 1 gram of this isotope is present initially, how long will it take for 80% of the lead to decay? (round your answer to two decimal places.)