I, i’m pretty sure sorry if it’s wrong
They would have the magnetic parts of the rocks oriented differently. This leaves a trace that allow scientists to find out how often this actually happens (as far as I remember, it's on average once in 800 000 years)
The fluid that is being passed through the syringe and needle is incompressible, which means that it will transmit pressure equally. Therefore, the pressure on the plunger will be equivalent to the pressure on the needle. We also know that:
Pressure = Force / Area
Pressure on plunger = 4 / (π*(0.012/2)²)
Pressure on plunger = 35.4 kPa
Pressure on needle = 35.4 kPa
35.4 kPa = F / (4 / (π*(0.0025/2)²)
F = 0.17 N
The force on the needle is 0.17 N