Q&A: Review Questions for Quiz Tmrw

[Obsessive123]

Got a quiz tmmrw and i want to know what the answers to these review questions are. :D


1.-The total consumption of electrical energy in the US is about 1.5 x 10to the11th Joules per year.
a. what is the average rate of electrical energy consumption in watts?
b. If the population of the US is 300 million, what is the average rate of energy consumption per person?
c. the sun transfers energy to the Earth by radiation at a rate of approx. 1.0 kW per square meter of surface. If this energy could be collected and converted to electrical energy, how great an area (in square meters) would be required to collect the electrical energy used by the US?

2.- An airplane passenger carries a 230 N suitcase up the stairs, a distance of 4.2 meters along the staircase (assume a 40 degree angle for the staircase).
a. How much work does the passenger do?
b. The same passenger disembarks and carries the suitcase back down the stairs. How much work does the passenger do on the way down?
c. Assume that the trip up the steps took 8 seconds. How much power did the passenger create in watts AND in horsepower on the way up?

 

[hage567]

Show what you've tried. Where are you stuck? What equations do you think you should use? We need to see your work.

 

[ogb p]

A: Hi there!

1a. The average rate of electrical energy consumption in watts would be 1.5 x 10^11 J/year divided by the number of seconds in a year (3.15 x 10^7 s), which equals approximately 4.76 x 10^6 watts.

1b. To find the average rate of energy consumption per person, we would divide the total consumption by the population, which would be 1.5 x 10^11 J/year divided by 300 million people, equaling approximately 500 watts per person.

1c. To calculate the area required to collect the electrical energy used by the US, we would divide the total consumption by the rate of energy transfer from the sun (1.0 kW/m^2). This would give us an area of approximately 1.5 x 10^11 m^2.

2a. To calculate the work done by the passenger, we would use the formula W = Fd cosθ, where F is the force (230 N), d is the distance (4.2 m), and θ is the angle of the staircase (40 degrees). This would give us a work of approximately 717.4 joules.

2b. The work done by the passenger on the way down would be the same as the work done on the way up, but with a negative sign, since the force is acting in the opposite direction. So the work done on the way down would also be approximately 717.4 joules.

2c. To calculate the power created by the passenger, we would use the formula P = W/t, where W is the work done (717.4 J) and t is the time (8 seconds). This would give us a power of approximately 89.7 watts. To convert to horsepower, we would divide by 746, giving us approximately 0.12 horsepower.

I hope this helps! Good luck on your quiz tomorrow! :)