# Thread: Algebra/Physics problem - kinematics

1. A light plane must reach a speed of 33 m/s for takeoff. How long must the runway be if the plane has a constant acceleration of 3.8 m/s2 ?

so, I am new to kinomatic equations. We are using the 4 Basic ones.

need to see this one worked out if I may.

Thanks

2.

3. What is the target variable? That is, what is it for which you're trying to solve?

distance?

5. What is it that you are given? And how may we relate these values?

6. Another way of saying what MarkFL said is this: can you write down a relevant, correct equation involving the target variable of distance?

7. Originally Posted by mathkid3
A light plane must reach a speed of 33 m/s for takeoff. How long must the runway be if the plane has a constant acceleration of 3.8 m/s2 ?

so, I am new to kinomatic equations. We are using the 4 Basic ones.

need to see this one worked out if I may.

Thanks
I think the OP meant the kinematic equations, 4 basic ones meaning:

1) x=x0+V0t+1/2at2
2) V=V0+at
3) a=constant
4) V2=V02+2a(x-x0)

If this is the case, the answer is a matter of determining starting values.

We can assume that the plane starts off at point 0 on the runway meaning that x0=0. we can also assume that the plane's initial velocity is 0, V0=0 (before moving). now we are given the acceleration, a=3.8m/s2, and final velocity, V=33m/s. From this we can find how long it will take the plane to reach the final velocity, using equation 2:

33m/s=0+(3.8m/s2)t
t=(33/3.8)s

Now that we have a value for t, we can use equation 1 to find the total runway length, x, required to reach takeoff speed:

x=0+0(t)+1/2at2
=(1/2)(3.8m/s2)((33/3.8)s)2
=143.30m

therefore the minimum amount of runway needed to reach the plane's necessary takeoff speed is 143.30 meters.

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