Rogowski style
When fucking someone you calculate the forces involved in each hump in newton's. you can use a=v/t to find acceleration, and f=ma to find the force applied in newton's. This is the only form of sex which involves math and measurement.
I just splooged 50 millilitres into her pussy at 2m/s^2, the load continued a further 2 inches. What is the coeficiant of friction? let's calculate this Rogowski style!