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

AI Thread Summary
To calculate the average power of a car accelerating from 0 to 100 km/h in 4 seconds, the change in kinetic energy must be divided by time. The formula used should convert the speed from km/h to m/s for accurate results. The correct average power calculation yields 121 kW when using appropriate units. The primary error identified in the initial attempt was the use of incorrect units, which led to an incorrect power calculation. Understanding the relationship between work, force, and power is essential for solving such physics problems accurately.
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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