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

[thereddevils]

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

 

[Fragment]

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.

 

[RTW69]

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.

 

[Cyosis]

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.