|
|
| *Vultures Knob>>>Bike Pedals |
Can YOU help me? |
I turn my bicycle up side down & turn the pedals so fast the back wheel spin .I hold a piece of card close to the back wheel. The spokes hit the piece of card & I hear a I hear a "musical" tone. (a). Explain why the card makes a"musical" tone. (b). Describe the energy change that occurs as the wheel slows down. (c). Describe and explain what will happen to the pitch of the "musical" tone as the wheel slows down. A Due to the stiffness of the spokes when stuck by the card a force is applied and the spokes vibrate causing noise for a short period of time. The card doesn't make a "musical" tone its the spokes if it can be called musical!!! B The wheel energy will reduce due to the impact of the card (and bearing friction) hence the velocity will reduce Energy =陆mv虏. Some of the energy will have been converted to sound, heat in bearing friction but most through the card. C As the wheel slow down the impact duration will increase and will result in the spokes vibrating at lower frequencies producing a different note. This all assumes the card hasn't changed position from the first impact i.e. the applied force is not a constant with an increasing differential in negative acceleration of the wheel. A few more tips you should probably mention momentum (m1v1,=m2v2) and the time period difference between each contact with different velocities although this doesn't change the note much i.e. if you hit every other spoke I doubt it will sound any different if the velocity of the wheel were to be the same. I'm not doing all your homework, This could get fairly complicated if you wanted to consider the rim stiffness, hub stiffness, bearings, difference is spokes tension manufacture tolerances, the effect of the inner tube and tyre acting as a damper, gyroscopic forces, the centre of mass being out etc. But I doubt your physics teacher would understand It's obvious. Do your own homework. a) the card is vibrating against the spokes of the wheel and producing longitudinal sound waves. b) kinetic energy is compounded by air resistance as well as the constant force of the card against the wheel c)The pitch gets lower as the number of impacts and consequentally vibrations per second decreases, GET SOME ELSE TO DO. Wait now......... How does the back wheel turn again?!! how on earth are you considering it 'musical'. the impact of the card on the spokes causes sound waves which is making the noise friction from the card causes energy inefficiency which makes the wheel slow down the 'pitch' wont change. the hits will just get further apart as the wheel slows down You will hear a very high pitch tone ,in fact it will be a scream if it is your fingers inst ed of the card ,don,t be a fool stop doing it . |
| Tags |
| Bike Repair Bicycle Shop Bike Tours Trail Map Bike Pedals Bike Lock Bike Lights Bike Helmet Quad Bike |
Bike Categories--Copyright/IP Policy--Contact Webmaster |