ElectricPavlov

I'm sorry...I am still a little unclear.    From the digram you have drawn, is she saying the angle between the sliding cable and the first arm is 60 degrees   and the angle between the two arms is 60 degrees and the angle between the second arm and the cable is also 60 degrees? (meaning one arm is longer than the other)  Do I have that correct?    I'm pretty sure I still need the angle of the sliding cable.....is it 30 degrees as your diagram is labeled?

  The tensions in the two arms will be different from each other.    The magnitude of the  horizontal components must equal each other in opposite directions and the vertical components of the tension in the two arms must sum to the weight of the car (7600kg)....I do not think I can calc that until I have the angle of the sliding cable and clarification of  the  60 degree angles...

   Hope I am not making this muddier than it really is supposed to be! 

If you know the current draw of the motor , it might be simpler to in-line a resistor with the motor and skip the IC... (like a 20 ohm resistor if your motor draws 200 mAmp)

FYI from the  7805 spec page   ( you might want to read it over)

https://electronicsforu.com/resources/learn-electronics/7805-ic-voltage-regulator

The greater the difference between the input and output voltage, more the heat generated. If the regulator does not have a heat sink to dissipate this heat, it can get destroyed and malfunction. Hence, it is advisable to limit the voltage to a maximum of 2-3 volts above the output voltage. So, we now have 2 options. Either design your circuit so that the input voltage going into the regulator is limited to 2-3 volts above the output regulated voltage or place an appropriate heatsink, that can efficiently dissipate heat.

See:

https://web2.0calc.com/questions/pls-help-fast_1

+ 9v     goes to the IC (input)  and the   cooler +

-  9v    terminal gos to the 'ground' of the IC and the cooler -

'output' of the IC goes to the fan......then the other end of the fan gets connected to the ground (-9v wire) also.....

    I do not have access to a scanner right now.....hope you can draw it....

Hope your battery has enough 'oomph' to run the cooler and fan and IC.    The IC has a max output of 5v 1 amp......hope your fan requires less than 1 amp.

I do not think you will have good luck with that.    Running the peltier at lower voltage than spec means you will not get the spec'd cooling from it......this may be ok for your application....but not good if you need the specified amount of cooling. Shortened component life would be expected if inadequate cooling is supplied.   Running the 5 v fan with the 9 volt battery will likely work for a short while (perhaps very short while) until something burns.     Get a 12 v battery and a 12 volt fan or run the fan with a resistor in-line with it to limit current .

My 2 cents.     You can always experiment ...if you can afford some fried components.    Others may be much more knowledgeable on this forum.

We answer physics probems all the time (when we can)....post on!  

If hanging cable makes 60 degrees with sliding cable.....how can sliding cable be at 30 degrees ?      That would make hanging cable at -90 degrees....which it is not.     Need actual sliding cable degrees..........or the degrees between the hanging cables.   Do you have the correct numbers?

The size of your graph paper.           JK