Calculate k-Value for Car Drag Equation with Given Data

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SUMMARY

The discussion focuses on calculating the k-value in the drag equation Fdrag = k*v^2 for a car with a mass of 1430 kg. The car operates at a maximum power of P = 60W at speeds of 120 km/h or above, while a power of P = 57W is observed between 30 km/h and 120 km/h. The user attempts to derive the k-value using the relationship between power, force, and velocity but encounters difficulties in achieving a consistent result. The provided data includes time and velocity measurements, which may be relevant for further calculations.

PREREQUISITES
  • Understanding of the drag equation Fdrag = k*v^2
  • Basic physics concepts related to power (P = F*v)
  • Knowledge of unit conversions (km/h to m/s)
  • Familiarity with algebraic manipulation of equations
NEXT STEPS
  • Learn how to convert velocity from km/h to m/s for accurate calculations
  • Study the relationship between power, force, and velocity in physics
  • Explore methods for deriving coefficients in drag equations
  • Investigate the impact of mass on drag force calculations
USEFUL FOR

This discussion is beneficial for physics students, automotive engineers, and anyone involved in vehicle dynamics or performance analysis, particularly those interested in drag force calculations and power management in vehicles.

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. :(
 
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No ideas? :(
 

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