Physics 161 First Homework Assignment

Some basic physics stuff:

• Masses are in units of kilograms
• Velocities are in units of meters per second
• Distances are in units of meters
• g, the gravitational acceleration of the Earth is 10 in units of meters per second per second
• Energy in the meters, kilograms, seconds system is in units call Joules

Questions:

1. You have flashlight that is powered by 2 1.5 Volt batteries. The wattage on your flashlight bulb is 5 Watts. What is the current flow (in amps) to the light bulb? To achieve this current flow, what resistance must exist in the lightbulb circuit?

2. Speaking of the batteries that you buy at the store, give a brief sketch of how they actual work in terms of energy storage and transfer. That is, what actually is a battery and how does it work?

3. Its likely that you will have to use the Web to find this information. For the City of Eugene determine the following:

• How much energy (in units if KWHs) does Eugene typically use in one day?
• What is the rate charge to the consumer per KWH? Compare this rate to that which exists on the East Cost.
• Where does Eugene get is electricity from?
• Approximately how many substations are there in Eugene (if this proves too difficult to determine).
• Send some email to George Hecht Director of the UO Physical plant and ask him what the typical daily energy consumption of Campus is. From that , determine the annual UO energy bill.

4. What is the kinetic energy of a 20 kilogram mass which is moving at velocity of 200 meters per second? To achieve an equivalent energy, how high above the earth would this object have to be? If you dropped the object and assumed no air resistance, what would the impact velocity be when it hit the ground (hint: use energy conservation).

5. You pay 10 cents per kilowatt hour. How much money does it costs to leave a 100 watt light bulb on for 48 hours? How much does it cost to leave a 400 watt heat lamp on for 1 hour?

6. Your stereo draws a current of 12 amps from your standard household outlet of of 120 Volts. How much power does your stereo radiate? What value of resistance must it have. How much does it cost to leave it on for 24 hours (assuming a cost of 10 cents per kilowatt hour.

8. Internet Required Alert Find some information on the Internet which refutes the claims to be made in this class that we will run out of Oil in the next 50 years.

9. Internet Required Alert The issue of Electro-Magnetic Fields (EMF) and human health has now assumed the status of an urban legend. Urban Legends are often borne from a small grain of truth which is then magnified by the "X-files" phenomenon - that is the wholesale belief that people have in conspiracy theory.

Below are two comprehensive sites that present objective data on EMF and human health. Visit each of these two and summarize what you think their findings are saying about exposure to EMF and the risk of cancer.

• NIH Site
• EMF Studies Summary Site

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