- #1

Like Tony Stark

- 179

- 6

- Homework Statement
- In the picture, the coefficient of static and dynamic friction for all contact surfaces are ##0.4## and ##0.14##, respectively. The mass of ##A## is ##73 kg## and the mass of ##B## is ##22 kg##. Determine the maximum force so that B doesn't slide. Then, suppose that the force applied to the system is greater than the force calculated previously, how much time would it take for the blocks to move ##10 m##?

- Relevant Equations
- Newton's equations

Well, I'm having trouble with the free body diagrams. For ##A## we have

##y)## weight, normal force, contact force with ##B##, ##F . sin(36.8°)##. And the acceleration is ##0## because we want to calculate the maximun force before moving.

##\Sigma \vec F = m . a_y##

##\vec N_A + \vec F . sin(36.8°) - \vec W_A -\vec Fc= 0##

##x)## ##F . cos(36.8°)##, friction force with the ground and friction force with ##B## and the acceleration is 0.

##F. cos(36.8°) - Fr - Fr_B=0##

##Fr## and ##Fr_B## have the same direction, don't they? Because the friction with ##B## must be pushing ##B## towards, and then the reaction force is in the opposite direction.

For ##B## we have:

##y)## weight and contact force (normal force)

##\vec N_B - \vec W_B =0##

##x)## friction force with ##A##

But is this force pointing to the right? And then, is the string applying a force on ##B##?

And then when I want to answer the second question, do they move equally? I mean, if ##A## traveled ##10 m## so did ##B##

##y)## weight, normal force, contact force with ##B##, ##F . sin(36.8°)##. And the acceleration is ##0## because we want to calculate the maximun force before moving.

##\Sigma \vec F = m . a_y##

##\vec N_A + \vec F . sin(36.8°) - \vec W_A -\vec Fc= 0##

##x)## ##F . cos(36.8°)##, friction force with the ground and friction force with ##B## and the acceleration is 0.

##F. cos(36.8°) - Fr - Fr_B=0##

##Fr## and ##Fr_B## have the same direction, don't they? Because the friction with ##B## must be pushing ##B## towards, and then the reaction force is in the opposite direction.

For ##B## we have:

##y)## weight and contact force (normal force)

##\vec N_B - \vec W_B =0##

##x)## friction force with ##A##

But is this force pointing to the right? And then, is the string applying a force on ##B##?

And then when I want to answer the second question, do they move equally? I mean, if ##A## traveled ##10 m## so did ##B##