HW solutions

Charge HW to submit on Friday


1.      What exactly IS charge?  How do we think of it?  How does it relate to protons, electrons, etc.?

 A way of quantifying how particles interact with each other, based on the amount (and imbalance) of protons and electrons.  Neutrons have zero charge.  Electrons have opposite charge relative to each other.

2.      Which particles in an atom are easiest to move, and why?

Electrons, as they are "around" the nucleus of the atom.

3.      What does atomic number (H = 1, He = 2, etc.) mean?

The number of protons in the nucleus of the atom. 

4.      What are quarks

 Fundamental particles, incapable of being broken up further.  There are 6 types, 2 of which (up and down) make up protons and neutrons.

5.      Coulomb’s law is an “inverse square law” – what does this mean?

The force varies as the inverse of the distance squared - as the distance between charges gets bigger, the force gets significantly weaker.

6.      Why does a charged balloon stick to the wall?

If we assume that the balloon has excess electrons (for a net negative charge), those excess electrons repel electrons from the surface of the wall (leaving a local positive charge).  The balloon now attracts the "locally" positive wall.  Excess electrons on the wall typically go to the ground.

7.      What is the fundamental law of electrostatics?

Opposites attract; likes repel.

8.      If I double the distance between two charged objects, how does the force between them change (if at all)?

The force weakens to 1/4 the original amount.

9.      How many excess electrons are in -10 C of charge?

-10/(-1.6 x 10^-19) = 6.25 x 10^19 electrons 


10.  Two clusters of charge, 2 x 10^-6 C and -4 x 10-6 C are separated by a distance of 0.1 m.  Use Coulomb’s law to calculate the force between them, and determine if this force is attractive or repulsive.


- 7.2 N



Comments

Post a Comment

Popular posts from this blog

Pendulum homework for Monday

In these problems you will need the formulas for the period of a simple pendulum AND the rearranged version (solving for L) we worked out in class. 1.  What is the period of a 1-m long pendulum?  Do you remember the historical significance of this particular length of pendulum?  If not, look back in your notes from the first few days of class. 2.  If you want a Grandfather clock to swing with a 1-second period, how long should the pendulum be inside of it? 3.  Calculate the experimental length of the giant swing, assuming that someone took 2.8 seconds to swing from rest on the platform to the opposite side of the swing (on the left).
Read more

HW related to pendulum lab

1.  Graph period of ONE swing (T, in seconds) vs. length (L, in meters).  T will be on y-axis and L will be on x-axis.  Make certain that length is converted to meters (if you used cm). 2.  Print out graph. 3.  Make a third column of data - square root of each length measurement (in meters). 4.  Think/write about this:  What makes a simple pendulum "simple"?  What is assumed to be true about the simple pendulum? 5.  If you have the video from the giant swing, try to determine the period of one oscillation (one complete swing of the person).  We are going to try to compare theoretical pendulums to the giant swing in our next class.
Read more