# Tagged Questions

2answers
178 views

### Mechanics Question: Energy, Work and Power

I'm a pure mathematician by trade, and have been trying to teach myself A-level mechanics. (This is not homework, it is purely self-study.) I've been working through the exercises and have come up ...
6answers
335 views

### Confused about unit of kilowatt hours

So I am a little confused on how to deal with the Kilowatt hours unit of power, I have only ever used Kilowatts and I have to design a residential fuel cell used as a backup generator for one day. ...
1answer
76 views

### What are the properties and impediments of a liquid air fueled engine?

I recently came across a very interesting article that suggested the possibility of using liquified gases like air, nitrogen, or oxygen as a power source for cars. It appears that this company is ...
0answers
93 views

### Energy efficiency Vs power efficiency

I want to understand if there can be any real difference between the requirement of Energy efficiency and the requirement of power efficiency for a physical system. For example for CMOS-based digital ...
1answer
108 views

### Inefficiency Comparison of Car Air Conditioning vs. Open Windows

On a recent long, hot journey in Spain, I was pondering which was the most efficient way of cooling the car. Which of these would be the most effective? Switching on the air conditioning, thereby ...
1answer
92 views

### Do you think it’s possible to make a power plant of the described kind?

We are working on a science project and try to engineer a power plant of a new kind. It is called Air HES (air hydroelectric station). The idea is described on our website. Do you think it is ...
1answer
453 views

### How are the CPU power and temperature caculated/estimated?

From Wikipedia The power consumed by a CPU, is approximately proportional to CPU frequency, and to the square of the CPU voltage: $$P = C V^2 f$$ (where C is capacitance, f is ...
1answer
67 views

### is it possible to gain from charging cold battery

Is it possible to get higher load of energy into a battery if you charge it when its cold eg. +9C? the battery is emptier, but does it let the power in? Is it safe?
2answers
304 views

### How can you measure battery output to see if the wattage is accurate? [closed]

When you have a battery and it shows you the milliamperehours and volts. You can use those to calculate the wattage. How can you test the battery to see if its wattage is accurate or if the company ...
1answer
118 views

### What are some ways that humans could have influence over what sequence a star was in?

How would a society go about either preventing our sun in its primary sequence from going into a Red Giant a billion years from now? Or perhaps, accelerating the process of going from main sequence ...
1answer
190 views

### Lifetime of battery

If I directly connect two terminals of 3V battery (negative to positive) using copper wire, would it lose all its charge faster compared to another 3V battery that is used to lighten a 1.5V bulb?
2answers
299 views

### What is a single word that describes the idea of the second time derivative of energy?

I think about position, its time derivative speed, and its second time derivative, acceleration. I would like to identify a single word that can be used as a handle for the second time derivative of ...
0answers
57 views

### A mixture of motion, circular motion and energy, please help, i didn't understand this problem, can anyone help? [closed]

A 20 W electric motor is being used to catapult a small ball of mass 0.5 kg, through a circular loop. The motor wind a thin thread on a pulley. The thread compresses the spring on which the ball ...
3answers
9k views

### Charging 12V 150Ah battery

I want to charge a 12V battery of 150Ah with a solar panel. The solar panel specs is 12V, 25 Watt. Can anyone please provide me how to calculate that how much time it will take to charge the battery? ...
1answer
309 views

### What type of solar energy technology has the most future potential?

In terms of dollars per watt, using theoretical efficiency limits, what technology holds the most promise to become the primary solar energy capture technology? My hunch is carbon-based modules, ...
1answer
2k views

### How to calculate fuel consumption of car (mpg) from speed and accleration knowing mass, drag coeff and rolling resistance?

How can I calculate the current (instantaneous) mpg of my car if I know the speed and acceleration of the car? From reading various answers for the "car going level or up/down hill" question asked ...
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