Reading values from Force Sensitive Resistor - Arduino
simulate this circuit &ndash; Schematic created using CircuitLab

Vo = V1* R2 /(R1+R2)

Total power Po = V1*V1/(R1+R2)

Adc unit (5V reference) = 5V/1023 ~= 5mV

Adc unit (1.1 internal reference) = 1.1/1023 ~= 1mV

No pressure R1 = 470 ohm:


Vo = 5*50/520 = 480mV ~= 96(5V) or 480(1.1V) ADC units 
Po = 25/520 = 48mW


No pressure, R1 = 10 kohm:


Vo = 5*50/10050 = 25mV ~= 5(5V) or 25(1.1V) ADC units.
Po = 25/10050 = 2.4mW


No pressure, R1 = 10 ohm:


Vo = 5*50/60 = 4.16V ~= 803(5V) ADC units.
Po = 25/60 = 0.41W


Same calculation for pressure applied until the sensor has 10 ohms:

R1 = 10 ohm:


Vo = 5*10/20 = 2.5V ~= 500(5V) ADC units.
Po = 25/20 = 1.25W, that's why the resistor is heating


It's better to put the sensor on the ground side because you can use 0 to no pressure voltage instead no pressure voltage to 5V then subtract the no pressure voltage. You also can use a lower reference for better resolution which is not possible with the sensor on the upper side since V0 will be higher than the reference voltage.

By using the internal reference you will lose the ratiometric output but the gain in resolution will compensate this.