# Thread: Integration word problem (last hw question)

1. ## Integration word problem (last hw question)

Last question and I'm done! And I'm also stuck, word problems are more of a sore for me than integrals.

1) On the moon the acceleration due to gravity is -1.6 meters per second. A stone is dropped from a cliff on the moon and hits the ground 20 seconds later. How high is the cliff?

2. Originally Posted by Hibijibi
Last question and I'm done! And I'm also stuck, word problems are more of a sore for me than integrals.

1) On the moon the acceleration due to gravity is -1.6 meters per second. A stone is dropped from a cliff on the moon and hits the ground 20 seconds later. How high is the cliff?
Ok there are a bunch of nice physics formulas called the kinematic equations which are great for this stuff, but I'm sure you're supposed to derive it through calculus.

So you start with $\displaystyle a = -1.6\frac{m}{s^2}$ . Integrate that dt and you should get $\displaystyle -1.6t + c_1$. What is C1? It's the initial velocity. You now have a velocity function. Integrate once more and you should get $\displaystyle \frac{-1.6}{2}t^2 + v_{0}t+c_2$. What is C2? That's the initial displacement. You now have a position function. Plug and chug.

How does that look?

3. Looks like solved. Thanks!