Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

hamza_b23 Group Title

Please help on related rates i do not get it A light is fastened on a rolling cart 1m above the floor. The light moves at 2m/s towards a 2m tall man standing 4m from a wall. How fast is the tip of the mans shadown on the wall moving when the light is 7m from the wall?

  • one year ago
  • one year ago

  • This Question is Closed
  1. hamza_b23 Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    @phi

    • one year ago
  2. Kelumptus Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    This resource will help you with these kinds of problems: http://www.intmath.com/applications-differentiation/4-related-rates.php. Generally the first step with these kinds of problems is to simply draw a picture. In this case the picture will look something like this:

    • one year ago
  3. Kelumptus Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1354327393530:dw|

    • one year ago
  4. Kelumptus Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    So what we have done in this picture already is that we have found the variables and the constants of the problem. The variables being x & y and the constants being the measurements given in the picture and speed that the cart is moving at. Note that the speed is given as -2. It is negative because as the cart moves closer to the man, x gets smaller. We will refer to the speed of the cart as: \[\frac{ dx }{ dt }\] (change in x with respect to t or time)

    • one year ago
  5. Kelumptus Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    The next step now is to build a mathematical relationship between x and y. Looking at the picture we can see that there is actually a triangle inside a triangle (see http://www.youtube.com/watch?v=1T9dHMU5pkk). So we can then say: \[\frac{ y-1 }{ 1 }=\frac{ 4+x }{ x }\] We say y -1 because we don't want to the first meter and we define y to start from the ground up, not from the height of the light.

    • one year ago
  6. Kelumptus Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    See how you go from here and let me know if you get stuck and i will give you some more help =)

    • one year ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.