Recent content by Pedro Delano

We can't calculate the work of the friction force? And then we discover the velocity just before impact by using the work-energy theorem. For this to work we must consider the initial velocity 90Km/h. Is it wrong?

There's no mistake, he just broke down the tension in x and y-direction. Try to draw a graph with two axes (x, y) and draw on it the decomposed tension in x and y-direction, the cage force (ma) and the weight force (mg), and you will see what the book did. I hope that someone more qualified...

Yes, I tried to solve the problem that way because of that exercise on the book, I was confused when I saw the solution, but I tried to see that force similarly to a force of friction made by the block. It seems that the solution is wrong, sorry.

Well, if there is a non-conservative force acting on a system (like friction force, or, in this case, the weight in x-direction), the relationship ΔKE = -ΔU is incomplete, because you need to add the work made by the non-conservative forces. The relationship becomes ΔKE + Workadditional = -ΔU...

The problem with the student solution is that he is ignoring the fact that the weight force of the block "A" is doing negative work. So the relationship ΔKE=−ΔU is not complete, in this case. What we need is to decompose the Weight of block "A" in the x-direction: WeightA = 9,81 N → Weight Ax =...

I'm a physics student in UERJ (State University of Rio de Janeiro), Brazil. As a lover of science, I wanted to be in a place were people discuss and do science, more specifically, physics, so here I am! Hope I can learn and help. :) OBS.: My english is not very good, so forgive the mistakes I...