Which of the following expressions is correct for force?

answer:

first

explanation:

according to the newtons 2nd law of motion,

the rate of change of momentum( δρ/δt ) is directly proportional to the unbalanced force applied and the momentum change takes place in the direction of the force.

so you can write,

f ∝ δρ/δt ⇒ f = k( δρ/δt )

by experiments scientist have found that k = 1

so you get your answer, f = δρ/δt

see earlier answer

do you have a formula possibly