What am I doing wrong?

  • Thread starter allergic
  • Start date
  • #1
11
0

Main Question or Discussion Point

Alright, so I've got this volume problem and it seemed really easy, only my answer is off, if only by a little bit. The problem is this: There is a tunnel, with a cross-section in the shape of a parabola, that is 5 meters wide and 10 meters high (I got the equation to be y=-1.6x^2 + 10). It takes someone driving 50 miles per hour 3 minutes to get through the tunnel (2.5 miles or 4023.36 meters). What is the volume of the tunnel? Well, i took the integral of y=-1.6x^2 + 10 from -2.5 to 2.5 and got 100/3. then i multiplied that by 4023.36 and got 134112 cubic meters. But my teachre says this is wrong. I used a different conversion, where the 2.5 miles equalled 4022.857 meters, and she said this was closer. Am i just off with my integration, or am I just crazy?
 

Answers and Replies

  • #2
HallsofIvy
Science Advisor
Homework Helper
41,833
955
I get 4022.5 m for the length of the tunnel. (One mile is 1.6091 km.)
 
  • #3
11
0
thanks! :)
 
  • #4
matt grime
Science Advisor
Homework Helper
9,395
3
I know SI units are slow to catch on in the US, and there's always the spelling issues, but it's "metres". Meters being something very different indeed, or have they decided to mix the spellings up?
 
Last edited:
  • #5
Zurtex
Science Advisor
Homework Helper
1,120
1
matt grime said:
I know SI units are slow to catch on in the US, and there's always the spelling issues, but it's "metres". Meters being something very different indeed, or have they decided to mix the spellings up?
In England the SI measuring unit for distance is indeed spelt "metres".
 
  • #6
Americans use "meters," but not "metres."

cookiemonster
 
  • #7
Njorl
Science Advisor
258
10
Zurtex said:
In England the SI measuring unit for distance is indeed spelt "metres".
In the US we spell "spelt" "spelled".
 
  • #8
165
0
Yes, that thing makes english a bit more difficut for people like me :)
 
  • #9
matt grime
Science Advisor
Homework Helper
9,395
3
both spelt and spelled are past tenses of spell, as mow can be mown or mowed depending on the case, but that's the problem of speaking a langauge that thinks it is latin when it is not.
 

Related Threads on What am I doing wrong?

  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
909
Replies
4
Views
5K
Replies
4
Views
2K
  • Last Post
Replies
17
Views
16K
Replies
3
Views
1K
Replies
1
Views
1K
  • Last Post
Replies
4
Views
789
Replies
2
Views
2K
Top