Physics 220 Class Exercise October 6 2000

Two objects of equal mass m are connected by a massless rope that does not stretch. One object lies on a flat table, while the other hangs over the edge, as shown in the diagram. The coefficient of kinetic friction between block and table is 0.5.

Draw a free body diagram for each object showing all the forces acting on each.

          Block on table                                                        hanging block

Choose a coordinate system for each diagram.

Fill out the table showing the components for the forces and of the acceleration in each diagram.
Block on table
Hanging block
Force x1-component y1-component Force x2-component y2-component
Acceleration Acceleration

Now apply N2 to each coordinate direction in each diagram.

How many equations do you have?

How many unknowns?

Use the connection between the two objects to write 2 more equations relating the accelerations of the two particles (1 equation) and the tension forces acting on each block (1 equation).


Finally use the relation between normal force and kinetic friction force to write another equation. Solve to find the acceleration of the hanging block.