Part of a playlist on basic dynamics problems: [ Ссылка ]

Constant velocity Atwood machine problem: find the force of friction on the sliding block.

In this Atwood machine problem, we are told the mass and pulley system moves at constant velocity, and this means that each mass has zero net force on it (otherwise they would be accelerating). In other words, the Atwood machine is in equilibrium!

We start by finding the tension in the string for the Atwood machine, and the tension is quickly obtained by analyzing forces on the hanging mass. Because the hanging mass is in equilibrium, the tension must be equal to the weight of the mass, and we obtain the tension.

Next, we analyze forces on the sliding mass, and we see that the tension must be equal to the friction force opposing the direction of slipping. We quickly find the kinetic friction on the sliding block in the Atwood machine, and we're done!

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