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Free Body Diagrams

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Lab Activities

Spacer The purpose of this lab is to give the students experience: (1) in applying Newton's Second Law and (2) in drawing and using free-body diagrams. The lab has three parts:

  • Pulleys: The students are given a set of pulleys, various pieces of lab hardware (bars, C-clamps, etc.), a set of hooked masses and a ball of string. With this equipment, they are asked to build an apparatus that will lift a mass while exerting a force equal to only a quarter of the mass's weight.

  • The Fairchild Elevator: Using a dial spring balance and 8 1-kilogram masses, the students are asked to determine the acceleration of the Fairchild elevator.

  • Circular motion: The equipment for this part consists of an air table with a hole in the center. In the hole is a pulley attachment. A string is run from an air puck on the table over the pulley and down through the hole. A hooked mass is suspended from the other end of the string underneath the table. The students are asked to launch the air puck in such a way that the puck travels in a circle and to calculate the centripetal force on the puck.

Course Level


Student Handouts


Number of set-ups available: 10

Per lab station:

2 large metal bars (~ 1 meter long)
2 medium metal bars (~2 feet long)
2 C-clamps
4 ring stand clamps
2 small hooked collars
4 200 gm hooked masses
4 100 gm hooked masses
1 spring balance (0-500 gm range)
1 ball of string
1 pair of scissors
1 single pulley with bar
1 single pulley without bar
1 double pulley
1 plastic tray to hold miscellaneous small items

One Setup Containing:

1 chair with a hard wooden seat
1 dial spring balance
8 1 kg slotted masses

One Setup Containing:

1 balance/standard mass set
1 large air table
1 pulley attachment for center of air table
1 air puck/washer style weights
1 large lab table with a hole in center (~1 in. in diameter)
1 air supply
1 air hose
2 hose clamps
1 pair of scissors
1 stopwatch
1 ball of string - small diameter
1 200 gm hooked mass
2 100 gm hooked masses
2 50 gm hooked masses
1 meter stick
1 roll of masking tape


Fairchild Elevator

Air Table


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