Prelab

For the mass hang experiment and for the crane experiment

- draw the free-body diagram

- resolve each force/tension into x and y components

 

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Pre-Lab Help

A proper free-body diagram shows the forces acting on a body, often considered at a single point. It is an abstraction ("free of any bodies") showing just the forces extending from a point (without showing pictures of the objects). Check your textbook as to how a free-body diagram is drawn.

- For the mass hang free-body diagram, show a single point indicating where the strings from the two scales and the hanging mass meet. Then show the forces extending from that point. Define angles with symbols on the diagram.

- For the crane free-body diagram, show a single point indicating where the meter stick, string from the scale and the hanging mass meet. Then show the three forces extending from that point that are from the hanging mass, the string tension and the tension in the meter stick. Define angles with symbols on the diagram.

- Also on the crane free-body diagram, show a fourth force due to the weight of the meter stick. This force acts in addition to the hanging mass and will be attributed to half of the meter stick mass ("half" as it divides evenly between the two end points from which the meter stick is held)

 
Resolving forces into xy components means writing equations for each force that look like F_x=... and F_y=...  ( not ΣF_x=... and ΣF_y=... ) and using trigonometry to resolve each force by using its angle shown on the free-body diagram. 

For translational equilibrium, one expects the sum of F_x forces to equal zero and the sum of F_y forces to equal zero.

Note: for this lab, it is strongly recommended that you bring your textbook.