This problem will reinforce concepts from class through a physical demonstration. Here's what you will
need: 1) string or something similar, 2) Scotch tape, 3) scissors, 4) camera or phone, and 5) paper with
your name written on it. Cut a piece of string approximately 2 feet in length. Find a door. Starting with
the door closed, tape one end of the string to the bottom corner of the door that is nearest to where the
door is hinged. Then, tape the remaining end of the string to the front of the door so that the string is taut
and forms a 60° angle with the hinged (vertical) edge of the door. Assuming that the corner of the door
where you first attached the string is the origin, define a Cartesian coordinate system such that the
threshold of the door is the x axis, the vertical hinged-edge of the door is y axis, and the z axis is positive
in the direction that forms a right-handed coordinate system (see section 2.5 of your textbook). Now,
swing the door from a closed position to open by 30°. Assuming that there is 0.25 lb of tension in the
string, and using the angles given in the problem and the length of your string, express the tension in the
string as a 3D Cartesian force vector directed from the origin outward. To receive full credit, include with
your written solution a picture of your setup with the paper containing your name appearing in the
picture.
