Deriving Expression for Average Drag on Object - Help Needed

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SUMMARY

The discussion focuses on deriving the expression for average drag on an object, specifically using the formula $$F_d = kv^2$$. The user attempts to calculate the average drag by integrating $$\frac{1}{t_f} \cdot \int_{0}^{t_f} k v^2 \hspace{1mm} dt$$, where $$t_f$$ represents the final time. A critical insight provided is the necessity of expressing velocity as a function of time, $$v(t)$$, to evaluate the integral effectively. The equation $$F = m \frac{dv}{dt} = -kv^2$$ is highlighted as essential for solving for $$v(t)$$.

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  • Knowledge of differential equations, specifically first-order equations.
  • Basic physics concepts related to motion and forces.
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  • Study the derivation of velocity as a function of time from the equation $$F = m \frac{dv}{dt} = -kv^2$$.
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lithium123
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I'm trying to derive an expression for the average drag on an object, which is in the form $$F_d = kv^2.$$ To find the average, I decided to use $$\frac{1}{t_f} \cdot \int_{0}^{t_f} k v^2 \hspace{1mm} dt$$where t_f is the final time. I'm having trouble evaluating this. Can someone give me some insight?
 
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To find the time average, you need the integrand to be a function of time.
So you need an expression for v(t) .
 
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Additional hint, there's a cool equation called
$$F = m {dv \over dt} ... = -kv^2$$

Can you solve for v(t) given than equation?
 
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