Did you measure the resistance of the sensor on the Prony Brake with 1 lb force applied using a multimeter across the sensor leads disconnected from power and the circuit ?
I don't believe your analog reading values. They make no sense. I want to see a photo of a multimeter displaying the voltage measured at the arduino analog input pin, with no force and then with 1 lb force.
Do you understand what is wrong with your whole setup ?
You have the ideal device (the Prony Brake) for this test yet you are not getting the voltages you should based on the resistance values you said you measured and posted.
What's wrong with that ? It's a simple resistance There is no way your analog readings (50 ..whatever) could be correct for a voltage divider consisting of 1 mega ohm and a variable pot with a range of 60k to 1 mega ohm. Do the calculations yourself. No matter how you wire the voltage divider , no matter which one is connected to Vcc or which one is connected to GND, the voltage measured across that voltage divider MUST BE in the range of approx 2.5V to 4.7V dc . So your reading of 50 represent a voltage of 0.244V. That is impossible. You need to measure the sensor and the resistor again without any connection to the circuit. There is no way you should ever get a reading less than 2V dc. You need to understand that because as far as I can tell, you still do not understand or even WHY . Google "voltage divider" . Do some calculations. Make a voltage divider circuit using the values you quoted to me and see what you read on your multimeter. You'll see there is no way you can read 0.244V dc with a voltage divider of those values. (1 M ohm and 60k to 1 mega ohm.