Suspended Block
Brief Description
This demonstration visually illustrates the resolution of forces on an incline by decomposing gravity into components parallel and perpendicular to the surface. Any force acting on an object with mass can be decomposed into two vector components. When any object is in contact with a surface, it experiences 2 main forces: its weight (Fg=mg) and the equal and opposite normal force. As this surface is raised by an angle θ, its weight can be decomposed into a vector parallel to the surface, and one perpendicular to the surface and parallel to the normal force. Equal and opposite forces are then applied to balance these components, allowing the system to remain suspended even when the incline is removed.
Materials
5 90° clamps, a 90° variable angle clamp, tall and medium wood blocks, 2 table clamps, sandpaper-covered board, 2 mass hangers with masses, 2 pulleys, the brick with string, incline support block, a small C-clamp, 2 big C-clamps, a long rod, 2 medium rods, and 2 small rods.
Setup
To set up this demonstration, stack the hollow wooden blocks to the desired height and place the sandpaper-covered board against them to form an incline. Clamp the incline support block to the table at the base of the board, then clamp the wooden blocks together and to the table. Attach the two medium rods to opposite sides of the table with table clamps and connect them halfway up using the long rod and two 90° clamps. Near the top of each rod, attach a short rod with a 90° clamp. Mount a pulley on each short rod, positioning them in line to the incline; use a variable-angle clamp on one side for finer adjustments. Attach the brick and string, run the string over the pulleys, and adjust the pulleys so the strings are perpendicular to the brick. Finally, hang masses from the strings. The required masses can be found by resolving the brick’s weight into components or by trial and error.
Performing the Demo
This demonstration does not require much to perform. Simply remove the incline and let the brick hang freely in the air.
Safety and Other Notes
To ensure that both strings are perpendicular to the brick, it might be smart for one to use a protractor or another angle measuring tool. Be cautious when the brick is suspended, as any disturbance to the string or masses may cause the brick to collapse.