# Thank you Ann (kinematics)

posted by
**eric (new chem or physics prob. in)**
.

Thank you Ann!

I had the equations and really was closing in on the answer... (stopping for 23 s is what really got me confused) in either case, the displacement for a) is 888 m !

Now I'll try to calculate (b).

Thank you much!

P.S. This is in response to my earlier physics (kinematics) questions.

A more pressing problem for which I have tried over and over again, with no results. I'm able to solve harder problems, but sometimes falter at really easier ones (depressing, I know). Here it is:

section Density and Atomic Mass

A major motor company displays a die-cast model of its first automobile, made from 9.35 kg or iron. To celebrate its hundredth year in business, a worker will recast the model in gold from the original dies. What mass of gold is needed to make the new model?

Look up the density of iron.

mass = volume x density.

You have the mass and density and you calculate volume of iron.

Then look up the density of gold.

mass = volume x density

Solve for mass. You have the volume from the previous calculation.

Gold: Density @ 293 K: 19.32 g/cm3

Atomic Mass: 196.96655 amu

Iron: Atomic Mass: 55.845 Amu

Density: 7.86

Density is mass per unit volume. The average density of an object equals its total mass divided by its total volume. The atomic mass of a chemical element is the mass of an atom at rest.

So for example, a statue made out of gold will be heavier than a statue made of iron because gold has a higher density.

density = mass / volume

watch your signs, density here is given in grams.