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Physics Doubt - Help please

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vanibharutham:
A wheel is connected to a motor and turned clockwise at a constant speed of 10 revolutions per second.  Two weights of 80N and 20N are hung from a string passing over the wheel.  With the wheel turning, the system is in equilibrium.  The length of string in contact with the wheel is 0.5m.  What power must the motor produce to turn the wheel?

What is the maximum power that you could achieve from a wind turbine that has a blade radius of 7m in a wind of velocity 5ms-1?

(Take the density of air as 1kgm-3)

Any help really appreciated

astarmathsandphysics:
Will answer in 2 hours

astarmathsandphysics:
A wheel is connected to a motor and turned clockwise at a constant speed of 10 revolutions per second.  Two weights of 80N and 20N are hung from a string passing over the wheel.  With the wheel turning, the system is in equilibrium.  The length of string in contact with the wheel is 0.5m.  What power must the motor produce to turn the wheel?

What is the maximum power that you could achieve from a wind turbine that has a blade radius of 7m in a wind of velocity 5ms-1?

(Take the density of air as 1kgm-3)

Any help really appreciated
Ignore the tuning wheel
For 20N T-20=(20/g)a (1)
For 80N 80-T=(80/g)a (2)
(1)+(2) 60=(100/g)a so a=3g/5 and from (1)T=20+(20/g)*3g/5=32
Distance moved by wheel in 1 second=0.5*10=5 and power=5*32=160J

Power =1/2mv^2=1/2*1*5*pi*7^2*5^2

staceyboy3:
Why do you use Power =1/2mv^2=1/2*1*5*pi*7^2*5^2 ...?

Where does all that come from?

astarmathsandphysics:
When i get home

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