AP Calculus help (2) (My solution provided)

[farealol]

I really tried to solve this, but for question b I only got one critical point at t=0, how can I solve for question c if I only have one critical point at (0,0)?

 

[lev888]

View attachment 19326

I really tried to solve this, but for question b I only got one critical point at t=0, how can I solve for question c if I only have one critical point at (0,0)?

View attachment 19327

Here's a rule of thumb that might be useful:
If your solution does NOT use ALL of the data given in the problem, there is a good chance you are missing something.
I never see textbook problems with extra info. Of course, real life problems are different

In this case you are told that mass depends on time. But your solution doesn't use this fact and the conveniently provided formula. Red flag!

 

[farealol]

This is what I did after all. Could somebody please see if it’s correct? The answer is still a little strange though.

 

[farealol]

Sorry I tried a few times so it’s really messy..

 

[farealol]

Here's a rule of thumb that might be useful:
If your solution does NOT use ALL of the data given in the problem, there is a good chance you are missing something.
I never see textbook problems with extra info. Of course, real life problems are different

In this case you are told that mass depends on time. But your solution doesn't use this fact and the conveniently provided formula. Red flag!

Thank you and I think now I fixed it.

 

[lev888]

Thank you and I think now I fixed it.

In a) why do you need t=...? You are asked to express energy as a function of time, not time as a function of something. Also, my point about mass applies to a) too, not just b).

 

[farealol]

In a) why do you need t=...? You are asked to express energy as a function of time, not time as a function of something. Also, my point about mass applies to a) too, not just b).

Oh I only focused on the rest of this question.. I’ll fix them. Thank you again.