Physics 161 First Homework Assignment

Date Due: Friday July 11
Turn in the Assignment via email to: ta@guernsey.uoregon.edu

Important Information: Since the campus network allows student-to-student communication and since this network is part of the on campus learning infrastructure, students should make use of it. Past experience shows that students won't make use of it unless they are assigned to do so. You may make use of the classroom discussion group to discuss this assignment amoung yourselves.
For this homework assignment, you are

REQUIRED

to collaborate with at least one other student. You can work in group sizes as large as 5. Each individual in that group could be assigned a particular question which would allow the group to complete the assignment in a more efficient manner.

OPTIONAL

If you want to prepare a web page in response to this assignment that would be great. This is not required however.

Some basic physics stuff:

Mases 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

1. What is the kinetic energy of a 10 kilogram mass which is moving at velocity of 20 meters per second?

2. What is the potential energy of a 10 kilogram mass which is suspended at a height of 20 meters above the earth's surface?

3. Suppose I have a 10 kilogram mass suspended at a height of 100 meters above the surface of the earth. Assuming no air resistence, what is the velocity of that mass when it hits the ground? (remember conservation of energy).

4. How much more energy can I get per kilogram of water from a hydroelectric facility which has a vertical drop of 90 meters compared to one which has a drop of 3 meters.

5. Suppose that your best friend has a mass of 80 kilograms and that you have positioned them on a frozen lake. While they are just standing there minding their own business, you carefully drive a crane up next to the frozen lake. On that crane you have a 20 kilogram wrecking ball. Using the crane like a pendulum you whack your friend as part of a physics experiment. If the wrecking ball is moving at 100 meters per second when it makes the impact - how fast will your friend be pushed across the lake? (assume the momentum of the wrecking ball is zero after the impact)

5. A lightbulb requires an amperage of 5 amps. You have a battery with a Voltage of 35 volts. How much resistance do you need to place in the circuit to deliver 5 amps to the lightbulb?

6. 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?

7. Your stereo draws a current of 2 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. What is the primary advantage of using a higher standard voltage, like the 220 Volts used in Europe?

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

10. Internet Required Alert Find some URLs that give good information about the Greenhouse effect and its implications for the planet.