Power output Definition and 134 Threads

Homework Statement A blue semicon LED is connected in series with a 10ohm series resistor to a voltage source. The LED emits 4.03 x 10^16 photons/s at a wavelength of 400nm. The current flowing through the LED is 40mA and the voltage across the LED is 3.5V. Calculate the power conversion...

Homework Statement Suppose your mass is 76.0 kg and you climb 40 stairs of height 18 cm in 19.0 s. What is your power output as you climb the stairs? Homework Equations Power = Work / change of time The Attempt at a Solution I need a hint on solving for the work. I tried solving for the...

Homework Statement A top fuel drag racer with a mass of 500.0 kg completes a quarter-mile (402 m) drag race in a time of 4.3 s starting from rest. The car's final speed is 115 m/s. What is the engine's average power output? Neglect friction and air resistance. Homework Equations P = W/T...

In the formula P=Tw, where T for torque(ftlbs) and w for angular velocity(rad/s), what is the unit for P(power)?

Homework Statement A battery supplies a steady current of 5.6 A for 21s. During this time 1410J of chemical energy is transformed into electric energy, but 560J of this electric energy is transformed into heat energy inside the battery. a) What is the emf of the battery? b) What is the...

The Earth has a surface temperature around 270 K and an emissivity of 0.8, while space has a temperature of around 2 K. Use Stefan's law: P(net) = 5.67×10-8 W/K4 m2 *A*e*(T4 - To4) to solve the following questions. (Radii of the Earth and the Sun are Re = 6.38×106 m, Rs = 7×108 m.) (a)...

Homework Statement 1. A wind turbine with a swept diameter of 20m and an efficiency of extracting energy from the wind of 40% is subjected to an average wind speed of 10m/s. (a) How much power might the turbine produce? Please can some one point me to the right equation as everyone I...

Hi I have a question to do with using PWM If for example I had a 1ohm load and a voltage supply of 4JC-1, I would get a power draw of 16JS-1, now if I had a duty cycle of say 50% I should get an average power output of 8JS-1. However if i thought of it as having an average current of 2CS-1 and...

I am trying to charge a battery using wind power! but i can't seem to find anything telling me how i can determine the power output coming from the generator, when all i know is the wind speed.. i know that the blades on the fan will have to be small but using the right gears with the high speed...

Homework Statement Rosie (mass 58 kg) pushes a box with a horizontal force of 170N (38.216 lb) at a speed of 16 m/min. What is Rosie's power output? Answer in units of W. Homework Equations Work/Time = Power MGH/T = Power .5MV^2 = Power The Attempt at a Solution 58(.2667...

Homework Statement The Sun emits electromagnetic waves (including light) equally in all directions. The intensity of the waves at the Earth's upper atmosphere is 1.5 kW/m2. At what rate does the Sun emit electromagnetic waves? (In other words, what is the power output?) The answer is...

A 2400 pound car ascends a 10 degree slope at 30 miles per hour. If the overall efficiency is 70 percent, the power output at 70 percent efficiency is 47.7 horsepowers. By the formula, Power=(force)(velocity) with 1 horsepower=550 ft*lb/s , the power output at 70% efficiency is 23.38...

Homework Statement A weightlifter is able to lift 250 kg 2.00m, in 2.00s. What is his power output? Homework Equations W=M x N P = W/Change t The Attempt at a Solution 250 x 2 = 500 (I thought that this was work) so then I divided by time (2.00s) to get power. The answer is not...

Homework Statement You lift a 40 kg weight vertically 2 meters in 2 seconds. Your power output is ____. Homework Equations The Attempt at a Solution M = 40 kg A = 1 m/s F = ? I have no idea how to go further than this. Also, what is power abbreviated as? For example, force...

Homework Statement A bicyclist coasts down a 7 degree hill at a steady speed of 5 m/s. Assuming the total mass of 75 kg, what must be the cyclist's power output to climb the same hill at the same speedHomework Equations power = force * distance / time force of gravity = mass * gravityThe...

A top fuel drag racer with a mass of 600.0 kg completes a quarter-mile (402 m) drag race in a time of 4.4 s starting from rest. The car's final speed is 115 m/s. What is the engine's average power output? Neglect friction and air resistance. I know: Power = Work/ change in time W = Force *...

Homework Statement Bob can throw a 500 g rock with a speed of 30 m/s. He moves his hand forward 1.0 m while doing so. a. How much work does Bob do on the rock? b. How much force, assumed to be constant, does Bob apply to the rock? c. What is Bob's maximum power output as he throws the rock...

Homework Statement The task is to compare the power outputs of solar cells, and solar panels. For solar cells, a circuit is devised to work out the power, solar panels a beaker of water is heated. Homework Equations Power=voltagextime Q=mc(delta)T Power=Energy/time The Attempt at a...

Homework Statement I am asked to plan a practical to determine the power output of a solar cell, i.e how much light energy is converted toe electrical energy per second. Now I thought(obviously) to just connect voltmeter across it with an ammeter and use PVI, however thinking about it, I don't...

Im trying to get to grips with factors? and want to check my methodology, so: It all about solar panels..I've calculated how much power the cell will produced @ AM1.5 this is 73 mW cm-2 . Now my question is, i have to calculate the short fall by a factor of 1000 due when its used indoors...

Hi, I need with the following question. Argon gas expands in an adiabatic turbine from 3MPa and 750 C to .2 MPa at a rate of 5 kg/s. Neglect KE and PE effects. Find maximum power output. I know I need to first find the temperature of state two and then use that to solve for h2 (I have...

Homework Statement The Sun emits electromagnetic waves (including light) equally in all directions. The intensity of the waves at the Earth's upper atmosphere is 1.4 kW/m2. At what rate does the Sun emit electromagnetic waves? (In other words, what is the power output?) ____ W Homework...

Homework Statement In the rope climb, a 68.4kg athlete climbs a vertical distance of 4.76m in 8.38s. What minimum power output was used to accomplish this feat? Homework Equations P_av=delta W/delta t P=dW/dt P=F*v The Attempt at a Solution Can someone help me get started on...

A bicyclist coasts down a 7.0 degree hill at a steady speed of 5.0 m/s. Assuming a total mass of 75kg (bicycle plus rider), what must be the cyclist's power output to climb the same hill at the same speed? I got 90N * 5.0 m/s = 450W but that is not the answer The book says 9.0 * 10^2 W i...

Hello, I am interested in finding out the electric power output from a compressed air system. i see that there is a formula for calc. it with the amount of compressed air required to generate about 1 W with a pressure of 1 bar is given by Compressed air(cu.mm/s) = (1000 N-mm/s) / (0.1...

The Sun emits electromagnetic waves (including light) equally in all directions. The intensity of the waves at the Earth's upper atmosphere is 1.4 kW/m2. At what rate does the Sun emit electromagnetic waves? (In other words, what is the power output?) I = P/A I know I need to convert...

Hi, if someone could help me figure this out I'd really appreciate it. Estimate the average power output of the Sun, given that about 1350 W/m^2 reaches the upper atmosphere of the Earth. I know the answer is 3.8 X 10^26 W but I don't know how to get there. I've tried different equations...

This question; A car takes 3s to acclelerate from to 0 to 50 km/h. Assuming constant power output from the engines and ignoring air resistance, how long does it take to go from o to 100 Km/h?, has been bothering me. I orginally assumed I could use the basic kinamatic equations but the power...

Hi there. Im afraid i know very little about electrical engineering:confused: , hence why I am here, but any help / direction / suggested reading would be much appreciated! Like i say, sorry if this is a completely stupid question:blushing: , but if you don't ask you don't get right? and who...

heres this question: theres a man who does 20 press-ups (ie facing down body straight) in 50 sec what is his power output? is it 20/50 = 0.4 press-ups per sec of power? i know power is in watts and its P = Fv = E/t if i take accleration to be 9.8 i could get v, a= (v-u)/t initial vel...

I tried getting some help before... but I couldn't figure out the logs- if anyone could help me (especially with the manipulation of the logs) I'd appreciate it. Here's the problem: 11) [3.0/4.0] A tornado warning siren on top of a tall pole radiates sound waves uniformly in all directions...

A person is making homemade ice cream. She exerts a force of magnitude 22 N on the free end of the crank handle, and this end moves in a circular path of radius 0.25 m. The force is always applied parallel to the motion of the handle. If the handle is turned once every 2.0 s, what is the...

How fast could a space based windmill turn when driven by the solar wind? Would such a device produce more or less energy than a solar panel of the same cost?

Hi! Estime the average power output of the sun, given that about 1350 W/m^2 reaches the upper atosphere of the Earth. the distance from the Sun to the Earth is 1.5 x 10^11m I have the formula E_o = [squ]2S/e_oc. This is what I have thus far... E_o =...