About Amy Expertise I love understanding how things work, especially when it comes to living
things. I`ve spent most of my life studying science and love passing on
this knowledge to kids. I currently work in a children`s science museum
where I`ve designed science exhibits on all sorts of topics; including
predators, music, weather, water, technology and much, much more! I`m
happy to answer questions about anything you have problems with at
school or help you with science projects. Also, I can help teachers
with ideas for classroom activities. Please note that I don`t answer
homework questions.
Experience I have an honours degree in Biochemistry and work as a science communicator for the National Science and Technology Centre in Australia.
Question I have seen various sites on the internet that talk about making a homemade anemometer using a ping pong ball (0.0025 kg?) supended from a 30 cm thread. See: http://www.enoreo.on.ca/resources/students/anemometer1.htm
Then you have a protractor on top and measure the angle that the wind blows the ball from the vertical. I was wondering how the values for angle vs wind speed or vertical distance the ball goes up vs wind speed can be calculated. I imagine the conservation of energy (potential and kinetic) would be used to calculate this. So I am look for a formula such as Angle = F(Wind Speed) or Distance Ball is raised = F(Wind Speed). I supect the Angle or the distance is a cubic funtion of the wind speed V. When the wind blows on the ball then the string angle is say Theta degrees. Then the ball is displaced L-LxCos(Theta). So the ball now has potential energy of MxGx(L-LxCos(Theta)) where L is the length of the string which in my case is 30cm. So then there is the kinetic energy of the wind which is equal to the mass of the wind times the square of the velocity divided by two. KE = MxVxV/2. The mass of the wind strinking the ball would be the air density x the volume I think. So that's about where I am at. The table below
I am helping my daughter in grade 5 to do a project relating to wind power. She does not need to know the formula but can do a table lookup like most people do. However I was interested in deriving the formula. I have a math background.
Answer Hi Ray,
Thanks for writing to me. I have to say that this question is out of my expertise. I've had a hunt around for other people who could help you and I suggest that you try these experts from the general (not science for kids)physics section in All Experts.
