It would be measured in newtons :)
Answer : B) The cow pulls back on the girl.
From newton’s third law we know that every action has a reaction force pushing back. So when the girl pulls on a cow, the cow is pulling back on her.
Answer:
K = 1.29eV
Explanation:
In order to calculate the kinetic energy of the proton you first take into account the uncertainty principle, which is given by:
(1)
Δx : uncertainty of position = 2.0pm = 2.0*10^-12m
Δp: uncertainty of momentum = ?
h: Planck's constant = 6.626*10^-34 J.s
You calculate the minimum possible value of Δp from the equation (1):

The minimum kinetic energy is calculated by using the following formula:
(2)
m: mass of the proton = 1.67*10^{-27}kg

in eV you have:

The kinetic energy of the proton is 1.29eV