Posted by **jm** on Friday, January 30, 2009 at 4:01pm.

The professor gave us no background material or explanations for any of these questions.

1. Imagine that molecules of H20 are stacked up in a cubic array, like a large number of cubical boxes. Each water molecule is taken to be at the center of each cube in this array. Let the side of each cube be L. Given that the density of water is I g/cm3, estimate the dis tance L. You are given that 18 gms of water contains 6.02 x 1024 molecules.

A. 6 angstroms

B. 1.44 x 10-8 cm

C. 14.4 angstroms

D. 3.0 x 10-10 m

Until this point I had never heard of/read about angstroms so I have no idea.

2.A student wishes to make a measurement of the road distance from his dormitory to the physics building of his university. she uses her car's trip odometer, which measures distance only in units of a tenth of a mile. She makes one trip, and the odometer reads 0.3 mi. What can she say is the distance ?

A. 3

B. 2

C. 1

D. 0

I put A, but that seems too simple. And the question is poorly written (he/she).

3. In the above problem to how many significant figures can she claim she knows the distance?

A. 3

B. 2

C. 1

D. 0

I put C.

4. In the same problem above if she has to know the distance to the physics department to the next significant figure how many round trips to the department should she take ?

A. 100

B. 10

C. 5

D. 3

None of these seem right to me. I wonder if the question should not read "round trips".

Thanks a lot!

- Physics -
**jm**, Friday, January 30, 2009 at 4:32pm
It didn't let me finish writing this.

For number 1, option D is 3.0 x 10-10 m.

For that question I got B.

2. A student wishes to make a measurement of the road distance from his dormitory to the physics building of his university. she uses her car's trip odometer, which measures distance only in units of a tenth of a mile. She makes one trip, and the odometer reads 0.3 mi. What can she say is the distance ?

A. 0.3 mile

B. 0.1 mile

C. 0.2 mile

D. 0.4 mile

I put A but it seems too simple.

3.In the above problem to how many significant figures can she claim she knows the distance?

A. 3

B. 2

C. 1

D. 0

I put C.

4. In the same problem above if she has to know the distance to the physics department to the next significant figure how many round trips to the department should she take ?

A. 100

B. 10

C. 5

D. 3

I'm stuck on this one.

- Physics -
**jm**, Friday, January 30, 2009 at 4:32pm
I'm just going to post this again since it keeps cutting my answers off.

- Physics -
**bobpursley**, Friday, January 30, 2009 at 6:05pm
correct on 1.

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