A person must move two heavy packages over a surface level so they place a 20kg package over a 30kg package and decide to move them together. The coefficient of kinetic friction between the lower package and the ground is 0.3. The person exerts a force of 400N at an angle of 36.87degrees from the horizontal.
Assuming that the upper package doesn't slide off the lower, determine the rate at which the accelerate.
I've never done/learned how to do a problem with an object on top of the other. Can someone please explain it and every step. Thanks!