JolleJ
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Homework Statement
You have to find the value of k in the drag equation; Fdrag = k*v^2
It is for a car driving. The motors maximal effect is P = 60W, and it uses this, when the car drives 120 km/h or above.
Previously, I have calculated that between 30 km/h and 120 km/h, the resulting effect is P = 57W. How to calculate the k-value with these two values?
The mass of the car is 1430 kg.
If it helps, there is also given a tabel of the time and velocity:
t: 0 2,2 3,1 5,5 8,9 13,3 18,9 (s)
v: 0 30 40 60 80 100 120 (km/h)
However, this was for one of the previous questions, not sure if it ought to be used.
Homework Equations
Maybe F*v = P ?
The Attempt at a Solution
I think I have to focuse on the time, where v = 120km/t. Here I know v and I know the two P's.
So I though of an equation like this:
60W - k*v^2*v = 57 W
However, this gives a very strange k, so I think I am wrong. :(