Hi i have been trying to find a pattern between friction problems in-order to help me answer different scenarios correctly, i hope you can help my understanding please. 1) A box that weighs 10.0 N is being dragged with constant velocity along a horizontal surface of the table by a rope that is at an angle of 45 deg with that surface. The tension in the rope is 5.0 N. What is the coefficient of friction? Ff= Friction force Fg= weight Fcosθ= component acting along the ramp Fsinθ= component acting perpendicular to the ramp (Normal Force) To calculate the Friction force we, Fg - Fsinθ In this case why do we substract Fsinθ from Fg to work out the Ff? 2) A 20kg box sits on an incline of 300. If the coefficient of sliding friction between the box and incline is 0.3 what is the acceleration of the box down the incline? Here, mgsinθ= weight acting along the ramp Fn the normal force = mgcosθ I found the formula which makes it simple to solve the problem, where Facceleration = mgsinθ - μkmgcosθ, with μk being the coefficient of kinetic friction. QUESTION: In this problem why is the normal force mg "cosθ" because in question 1) the normal force was Fsinθ, also why is the μk coefficient of kinetic friction associated with mgcosθ when i need to find the Facceleration. Also in this scenario can the Friction force be calculated the same way as question 1) by Fg - Fsinθ ? or is there a similar concept or way of finding it? 3) A 1200 kg car is coasting down a 30 degrees hill. When the car’s speed is 12 m/s the driver applies the brakes. What constant force F (parallel to the road) is required if the car is to stop after travelling 100m? In this scenario can we use the Facceleration equation from question 2) to solve the problem (Facceleration = mgsinθ - μkmgcosθ) or a=gsinθ? if not what is the reason for this? Overall Question Are all these above question very similar in the sense that they share a fundamental concept which can help me solve them? or any other friction related problems involving inclined ramps etc and horizontal surfaces. And is there a simple method to help solve problems when looking at inclined problems and non inclided problems. Thank you very much for any help guys i have been stressed out trying my best to understand friction related problems.