A factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25. (a) What magnitude of force must the worker apply?

Video transcript

Hey everyone Saturday. We're being told that in a certain theater, a 250 kg piano has pushed three m on a rough horizontal surface. The coefficient of kinetic friction between the piano and the surface is 0.4. And we're being asked to find the magnitude of the force needed to move the piano at a constant speed. Now, that last part is very important because that determines how we go about her answer. So if we need to move an object at a certain speed at a constant speed rather on a uh friction surface, well, that means that the force applied, the force used to push the piano. In this case the force applied must be equal to the force of kinetic friction. So this means that the force must be equal to the coefficient can make friction multiplied by the normal force. And we know that the normal force is just mass times gravity. Because we're uh dealing with a horizontal surface, we're not dealing with any verticality in this case. So solving this, we get that the coefficient of Kinetic friction is 0.4. The mass is 250 kg. And the um excuse me, the value of g the acceleration due to gravity is 9. m per second squared. So solving this, we get a final answer of 980 newtons. Therefore, the magnitude of the force needed to move the piano at a constant speed is answer choice. C 980 mutants. I hope this helps. And I look forward to seeing you all in the next one