What is the mass of a 3.00 cm^3 piece of gold having a density of 19.3g/cm ^3

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?

How much carbon is stored in the atmosphere as co2

+= + + balance the equation on coefficients, ex. 1,1,1