Answer each question completely with explanations of all answers. Show all calculations.
1. A 200 lb man walks out to the end of a uniform horizontal plank which projects
perpendicularly over the edge of a roof. The plank is 20 feet long and weighs 100 lb. How
far from the edge of the roof can the plank overhang?
2. A 10,000 kg truck cruises over a 30 m span bridge. What are the normal forces on the ends
of the bridge when the truck is 10 m from the right side, if the mass of the bridge itself is
ignored?
3. A uniform ladder 4 m long rests at 45-degree angle against a frictionless wall. If the ladder
has a mass of 10 kg, what is the frictional force at the base of the ladder? (Hint: make a free
body diagram and consider both trans. and rot. equilibrium.)
=
4. A uniform beam, of length L and m = 2.2 kg, is at rest with its ends on two scales. A
uniform block, with mass M = 3.6 kg, is at rest on the beam, with its center a distance,
L
from the beam’s left end. What do the scales read?
4
5. A uniform meter stick supported at the 25 cm mark is in equilibrium when a 200-gm rock is
suspended at the 0 cm end. Is the mass of the meter stick greater than, equal to, or less than
the mass of the rock? Explain your reasoning.