You are lowering two boxes, one on top of the other, down the ramp shown in the

Question

You are lowering two boxes, one on top of the other, down the ramp shown in the figure (Figure 1) by pulling on a rope parallel to the surface of the ramp. Both boxes move together at a constant speed of 13.0cm/s . The coefficient of kinetic friction between the ramp and the lower box is 0.431, and the coefficient of static friction between the two boxes is 0.772.

What force T do you need to exert to accomplish this?

What is the magnitude f of the friction force on the upper box?

What is the direction of the friction force on the upper box?

You are lowering two boxes, one on top of the other, down the ramp shown in the figure (Figure 1) by pulling on a rope parallel to the surface of the ramp. Both boxes move together at a constant speed of 13.0cm/s . The coefficient of kinetic friction between the ramp and the lower box is 0.431, and the coefficient of static friction between the two boxes is 0.772. What force T do you need to exert to accomplish this? What is the magnitude f of the friction force on the upper box? What is the direction of the friction force on the upper box?

Explanation / Answer

a) Imagine a very small force F , is applied to the upper block.
This will not be sufficient to slide the top block on bottom block.
But since table is frictionless, ANY force imparted to lower block will move it in relation to table.
As F increases a stage will be reached when the small block exceeds static friction.
f =

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