How Do You Calculate the Average Power of a Car in Physics?

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Homework Help Overview

The problem involves calculating the average power of a car with a mass of 1250 kg that accelerates from 0 to 100 km/h in 4 seconds. The context is centered around the concepts of kinetic energy and power in physics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between kinetic energy and average power, with one participant attempting to calculate power using the change in kinetic energy over time. Others suggest the need for unit conversion from km/h to m/s to yield correct results.

Discussion Status

There is an ongoing exploration of different methods to approach the problem. Some participants provide guidance on unit conversion and the calculation of acceleration, while others express concerns about the complexity of the proposed methods. Multiple interpretations of the problem are being discussed.

Contextual Notes

Participants note the importance of using correct units and the potential for misunderstanding in the application of formulas related to work and power. There is an acknowledgment of the original poster's confusion regarding their calculations.

thereddevils
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Homework Statement



A car o fmass 1250 kg accelerates from 0 to 100 km/h in 4 s . The average power of the car is ?

Homework Equations





The Attempt at a Solution



Though it looks simple , but i don see my mistake.

The average power is the change in kinetic energy over time ,

(1/2 x 1250 x 100^2)/(4)

is my working correct ? But that doesn't give the answer which is 121 kW
 
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For the formula to yield an answer in watts, you need to convert km/h into m/s. Divide the answer you get by 1000 to get an answer in kW.
 


You know the change in velocity and the change in time so you can calculate the acceleration. Knowing the acceleration and time you can calculate the distance the car travels. Knowing the mass of the car and its acceleration you can calculate the force on the car. Knowing the force and distance you can calculate the work done. Power equals work/ change in time.
 


RTW69 said:
You know the change in velocity and the change in time so you can calculate the acceleration. Knowing the acceleration and time you can calculate the distance the car travels. Knowing the mass of the car and its acceleration you can calculate the force on the car. Knowing the force and distance you can calculate the work done. Power equals work/ change in time.

This over complicates things quite a bit. The work is given by the difference of kinetic energy. thereddevils only mistake is the usage of the wrong units.
 

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