Average Power and speed of a car

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Homework Help Overview

The discussion revolves around calculating the average power required for a car to accelerate from rest to a final speed, focusing on the physics of motion and power. The problem involves a 2000kg car accelerating at 3m/s² to reach 20m/s.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between force, power, and velocity, with one participant attempting to calculate power using force and final velocity. Others raise questions about average versus instantaneous power and the implications of constant acceleration on average velocity.

Discussion Status

Some participants have offered guidance on understanding the distinction between average and instantaneous power, referencing relevant equations and concepts. There appears to be a productive exchange of ideas, with some participants expressing appreciation for the help received.

Contextual Notes

Participants are working within the constraints of a homework problem, with one expressing uncertainty about the relevant equations and another referencing a tutorial for clarification. The discussion includes a focus on the change in energy and the time taken for the acceleration.

nagaromo
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1. A 2000kg car, initially at rest, is accelerated along a horizontal roadway at 3m/s^2. What is the average power required to bring the car to a final speed of 20m/s?



2. I don't know the relevant equations :(



3. Well I first tried force multiplied by the final velocity which is 120000 watts, but that's not the answer. Please help!
 
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The velocity increases linearly if the acceleration is constant. What does that say about the average velocity as compared to the final velocity over the distance (or time) concerned?
 
nagaromo,
Take a look at this tutorial posted by Mr. Bernhardt, specifically page 99 that deals with the concept of power. Equation 5.54 is for instantaneous power, but the average power is given by the total change in energy(start to finish) divided by the total time.
Think about how the energy of the car changes(the work done) and how to figure out how long it takes for the change to occur.

The reason your first attempt was wrong is that you calculated the instantaneous power at the very end of the push, when the car was at it's final speed. You want the average, over the whole push.
 
oo now i got the right answer. thanks guy! i appreciate the help :D
 
60000w right? :d:d:d
 
That's the answer I got.
 
thanks! <3 :]
 

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