Two boxes are sitting on a frictionless ramp touching each other?
Two boxes are sitting on a frictionless ramp touching each other. You push on the lower box, parallel to the ramp. What is the force of one box on the other if you are pushing hard enough to have the boxes go up the ramp with a constant speed? I really have no clue with this one. Any help is really appreciated!
Physics problem about kinetic friction help?
You need to arrange all the forces in X (horizontal) and Y (vertical) directions. It is very similar situation on this picture. Only Fp should be on the left side of the crate (pointing left - in the oposite direction of Ff) with 25° angle above the horizontal. http://en.wikipedia.org/wiki/Friction Forces in your case are: Fp = pulling force Ff = frictional force N = normal force W = weight of the crate (m = W/g) - this is how you get the mass of the crate. ß = angle Ff = μk*N μk = kinetic friction I suggest to you that you draw all the forces. Vertical forces (there is no acceleration in vertical direction, that is why 0 is on the right side of the equation instead of m*a): N + Fp * sin(ß) - W = 0 N = W - Fp * sin(ß) N = 925 - 325 * sin 25° N = 787,65 N (newtons) Horizontal forces: Fp * cos(ß) - Ff = m*a Fp * cos(ß) - μk*N = m*a 325N * cos 25° - 0,25 * 787,65N = m*a 97,64N = m*a Now you need a mass of the crate: W = m*a m = W/g m = 925/9.81 m = 94,3 kg (mass of the crate) You return here again 97,64N = m*a a = 97,64N/94,3kg --> Note: 1N = 1kg*m/s^2 a = 1,035 m/s^2 Static friction is friction between two solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface. The coefficient of static friction, typically denoted as μs, is usually higher than the coefficient of kinetic friction. Kinetic (or dynamic) friction occurs when two objects are moving relative to each other and rub together (like a sled on the ground). The coefficient of kinetic friction is typically denoted as μk, and is usually less than the coefficient of static friction for the same materials. Example: Kinetic friction is when two objects are rubbing against each other. Putting a book flat on a desk and moving it around is an example of kinetic friction.