So now we're asked to derive the equation f is equal to ma. So to start this one off we use Newton's second law Which tells us that force is proportional to the rate of change of momentum So we can write that as force is is proportional to change of momentum over time And that then can be written as f is proportional to the change of momentum is m times the final velocity minus m times the initial velocity over t Now we can factor out our m here so f is proportional to m times v minus u over t Now v minus u over t. Well, that's just acceleration So now we have f is proportional to m times a mass times acceleration If we want to get rid of this proportionality sign and make that an equal sign we need to bring in our constant of proportionality So that would be f is equal to k which is our constant of proportionality times ma And k is equal to 1. I'll explain why that is in a second if k is equal to 1 That means f is equal to ma which is what we were asked to show in the first place Now y is k1. Well the force is 1 Newton if we define 1 Newton so f is equal to 1 Newton In this case if we have a force of 1 Newton that means we have a mass of 1 kilogram And we have an acceleration of 1 meter per second squared And if we sub in 1 1 and 1 into the equation here we get k is equal to 1 So that's the reason y k is equal to 1