Force applied to simple hand pump and resulting PSI

[fred_1985]

I hope I am asking this in the right forum.

Lets say you have a simple hand pump, similar to a bicycle pump, and you exert X amount of force on the handle. How do you calculate the resulting air pressure it creates out of the small valve at the end?

Obviously friction between the O-ring and inner wall of the pump is going to come into play, but a rough estimate would do.

Thanks.

 

[russ_watters]

Pressure is force divided by area. Force on the handle, cross sectional area of the piston.

 

[oswaler]

I would approach this question by first considering the principles of fluid mechanics and the ideal gas law. The ideal gas law states that the pressure of a gas is directly proportional to its temperature and the number of gas molecules present, and inversely proportional to its volume. In this case, the gas being pumped is air.

To calculate the resulting air pressure from the hand pump, we first need to know the volume of the air being compressed. This can be estimated by measuring the volume of the pump's cylinder and the length of the stroke of the pump handle. Let's assume a volume of 500 mL for the pump's cylinder and a stroke length of 10 cm.

Next, we need to consider the force being applied to the pump handle. This can vary depending on the strength and technique of the person pumping, so we will use a general value of 20 newtons (N).

Using the ideal gas law, we can calculate the pressure (P) of the compressed air:

P = (nRT)/V

where n is the number of moles of air, R is the universal gas constant, T is the temperature in Kelvin, and V is the volume of air.

Since the pump is being used in normal atmospheric conditions, we can assume a temperature of 298 K and a pressure of 1 atm. The universal gas constant (R) is 0.0821 L atm/mol K.

Now, we need to calculate the number of moles of air being compressed. This can be done by using the volume of the air (500 mL or 0.5 L) and the ideal gas law:

n = PV/RT

Substituting our known values, we get:

n = (1 atm)(0.5 L)/(0.0821 L atm/mol K)(298 K) = 0.0063 moles of air

Finally, we can plug in all of our values into the ideal gas law equation to solve for pressure:

P = (0.0063 mol)(0.0821 L atm/mol K)(298 K)/(0.5 L) = 0.985 atm

Converting to PSI (pounds per square inch), we get a pressure of approximately 14.3 PSI. This is a rough estimate and may vary depending on factors such as friction and the efficiency of the pump's design. However, it gives us a general idea of the pressure that can be generated by a simple