Throwing rocks on mars.

[Pi Man]

Hey I have another problem here. Apparently someone wants to go to mars just to throw rocks. Anyway, this is the question:

If a rock is thrown vertically upward from the surface of mars with a velocity of 15m/s, it's height after t seconds is h = 15t - 1.86t^2

What is the velocity of the rock when its height is 25 m on it's way up? On it's way down.

The answer says it is 6.24 up and 6.24 down

I don't know how it got that answer. I set both the derivative and the original equation to 25 and solved but I did not get that answer. What am I doing wrong? Can anyone help?

 

[tkhunny]

What did you get for 't' when you solved h(t) = 25?

Why would you want h'(t) to be 25?

 

[Pi Man]

What did you get for 't' when you solved h(t) = 25?

Why would you want h'(t) to be 25?

I got like 10 point something when I set h(t) = 25

If I new that, I wouldn't be asking for help.

 

[tkhunny]

I got like 10 point something when I set h(t) = 25

Please demonstrate this result. Your algebra skills should produce two values.

If I new that, I wouldn't be asking for help.

This is not a useful reply. If you REALLY have no clue, you are in the wrong class or you have not been attending (or other such catastrophic behavior). Just answer the question. Nonresponsive silliness helps no one. The THOUGHT question is intended to encourage you to THINK. If all you can think of is to punt, you will fail and there is nothing anyone can do about it. Please do better in any future exchange.

 

[Pi Man]

Please demonstrate this result. Your algebra skills should produce two values.



This is not a useful reply. If you REALLY have no clue, you are in the wrong class or you have not been attending (or other such catastrophic behavior). Just answer the question. Nonresponsive silliness helps no one. The THOUGHT question is intended to encourage you to THINK. If all you can think of is to punt, you will fail and there is nothing anyone can do about it. Please do better in any future exchange.

Divide by zero *****. That's how I roll.

 

[mmm4444bot]

That's how I roll.

If you are not willing to pay attention, then please go somewhere else for help.