[#142] How many cells are you? How many cells in a human? Assume that cells have a typical size of about 10 µm (1µm = 10-6 m) in all directions. And that we are the same density as water, and are made completely of cells (both exaggerations, of course, but fine for an order of magnitude estimate). Hints: What is the volume of a cell? What is the volume of a human? How can these quantities be related to give the number of cells in your body? The shape of the cell is not important in this rough estimate: for instance, the difference in volume fraction between say cubes and close packed spheres is only 26%. Format: When you enter your answer, enter it as a power of 10. For example: for 100000, enter "10^5". We'll use this notation later, too.

The common Eastern mole, a mammal, typically has a mass of 75 g, which corresponds to about 7.5 moles of atoms. (A mole of atoms is 6.02 * 1023 atoms.) In atomic mass units (u), what is the average mass of the atoms in the common Eastern mole?

We are going to make a simple approximation of the number of atoms in the universe. Assume all the atoms in the universe are hydrogen. (In actual practice, over 75% of the atoms in the universe are hydrogen.) Assume the sun is a typical star (made of pure hydrogen) has a density of 1.4 g/cm3 and is a sphere with a radius of 7.0*108m Assume that there are 100 billion stars in our Milky Way galaxy that are identical to our sun. Assume that there are 10 billion galaxies in the universe identical to our Milky Way galaxy. How many atoms are there in the universe?

Estimate the number of molecules that make up Earth, assuming an average molecular mass of 30 g/mol. (Note there are on the order of 1024 objects per mole.)

Spherical mirrors. Object O stands on the central axis of a spherical mirror. For this situation object distance is p; = +30 centimeters, the type of mirror is convex, and then the distance between the focal point and the mirror is 38 cm (without proper sign). Find (a) the radius of curvaturer (including sign), (b) the image distance i, and (c) the lateral magnification m. Also, determine whether the image is (d) real or virtual, (e) inverted from object O or noninverted, and (f) on the same side of the mirror as Oor on the opposite side.

(a) Calculate the approximate number of atoms in a single sheet of 0.01 lb paper. Note that a single carbon atom is about 2×10-26 kg in mass and 1 lb is approximately 4.448 N. (b) Estimate to order of magnitude the total mass of paper used by a typical class throughout a semester.

The habitable part of earth's surface has been estimated to cover 60 trillion square meters. Estimate the percent of this area occupied by humans if earth's current population stood packed together as people do in a crowded elevator.

The nucleus of an atom can be modeled as several protons and neutrons closely packed together. Each particle has a mass of 1.67 x 1027 kg and radius on the order of 10-15 m. (a) Use this model and the data provided to estimate the density of the nucleus of an atom. kg/m3

A typical person has an average heart rate of 71.0 beats/min. Calculate the given questions. How many beats does she have in 6.0 years? How many beats in 6.00 years? And finally, how many beats in 6.000 years? Pay close attention to significant figures in this question. 6.0 years: beats 6.00 years: beats beats 6.000 years: