Engine Performance(Finding Power)

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Homework Help Overview

The problem involves determining the power developed by a car's engine based on its acceleration from rest to a specified speed within a given time frame. The subject area includes concepts from mechanics, specifically relating to kinematics and power calculations.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss unit conversions and the implications of constant power on acceleration. There are attempts to apply kinematic equations and power formulas, with questions about the correctness of initial calculations and the relationship between force, velocity, and power.

Discussion Status

The discussion has evolved with some participants providing guidance on the relationship between work and power, while others have raised questions about the implications of constant power on the system's dynamics. There appears to be a mix of interpretations regarding the approach to solving the problem.

Contextual Notes

Participants are navigating the constraints of the problem, including the assumption of constant power and the need to calculate acceleration and work done within the context of the given parameters.

austin zitro
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Ok, here is the problem:
A car manufactuerer claims that their car can accelerate from rest to 101 km/hr in 5.6 seconds. The car's mass is 840 kg. Assuming that this performance is achieved at constant power, determine the power developed by the car's engine.
Part B) What is the car's speed after 2.8 s?

Ok, so first off i changed the 101km/hr to m/s. So it should be 28.1m/s. Then I used the equation: V=Vo + at to find acceleration and so plugging in 28.1m/s=0 + a(5.6s), a= 5.01m/s^2. So since power = F*v, I plugged in P = 840kg*5.01m/s^2*28.1 = 118256.04 W. This is not right. Since the power is constant, I'm thinking that the acceleration is probably not. So how would I incorporate that into my equation?? Once I get that, I can prolly get part B. Thank's for any help at all!
 
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Check those units are those the Power units?? also think about constant power what does that mean?
 
I ended up getting it. I used the equation P=W/t, where work = change in kinetic energy. Thanks for the help.
 
You know that
[tex]F = m \frac {dv}{dt}[/tex]
What can you conclude if Fv is constant?
 

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