What is the Solution to the Differentiation Problem for a Descending Plane?

[1875]

At time t = 0 and position s = 0 a plane starts its descent into an airfield. From this point, the distance s in km as a function of time t in hours is given by;

s = 300 + 400t - 200t^3

The inital velocity I have calculated to be 300 km/hr and the acceleration after 1/2 hr is 475 km/hr2. I am having problems with the last question;

c) the time to when the velocity is zero and the distance traveled in that time?

 

[hotvette]

So, what's the equation for velocity? Set it equal to zero and solve for t.

 

[1875]

I did this and came out with 0 = 400 - 600t^2

I had difficulty transposing this for t as I kept getting discrepencies. Once I have t I can do the rest, I am not even sure if the above equation is correct for velocity.

 

[hotvette]

I had difficulty transposing this for t as I kept getting discrepencies

What do you mean?

I am not even sure if the above equation is correct for velocity

It is.

 

[1875]

I came out with t = -400/600^2 but I wasnt confident with the number this came out to.

 

[Mark44]

Check your algebra. The solution of 0 = 400 - 600t² is not t = - 400/600².