SOLUTION: The power, P (watts), of a car engine is proportional to the square of its speed, k (m/s). When k=35, P=2200. Work out the power (to 1DP) when the speed is 40m/s Please coul

Algebra ->  Proportions  -> Lessons -> SOLUTION: The power, P (watts), of a car engine is proportional to the square of its speed, k (m/s). When k=35, P=2200. Work out the power (to 1DP) when the speed is 40m/s Please coul      Log On


   

Question 1137719: The power, P (watts), of a car engine is proportional to the square of its speed, k (m/s).
When k=35, P=2200.
Work out the power (to 1DP) when the speed is 40m/s

Please could you help me with this question. I have tried but I just really do no understand it. When I tried I got the answer of 0.6 watts. The site called Hegartymaths told me that it was incorrect and the video it comes with is not very understandable for me.
Thank You.
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

The power, P (watts), of a car engine is proportional to the square of its speed, k%28m%2Fs%29; it means if you have two different powers and speeds, you will have a proportion
P%3Ak%5E2=P%5B1%5D%3Ak%5B1%5D%5E2 or
P%2Fk%5E2=P%5B1%5D%2Fk%5B1%5D%5E2
When given:
k=35, P=2200
Work out the power P%5B1%5D (to 1DP) when the speed is k%5B1%5D=40%28m%2Fs%29
so,
P=2200
k=35
k%5B1%5D=40
and you need P%5B1%5D
2200%2F35%5E2=P%5B1%5D%2F40%5E2
2200%2F1225=P%5B1%5D%2F1600
1.79592=P%5B1%5D%2F1600
1.79592%2A1600=P%5B1%5D
P%5B1%5D=2873.5 watts