Q1: Observe
the coin on the binder. Before the coin slides, what kind of friction
holds it in place? Sketch what a microscopic veiw of the coin
and binder's interacting surfaces might look like. Continue tilting
the binder until the coin starts sliding. What is the name of
this new type of friction after the coin is moving and how is
it different? How would your sketch change?
Q2: Try
to determine the angle at which the coin exactly breaks free.
Is this possible? Why or why not? This is known as the Angle of
Repose for an object on a slope. What is the Angle of Repose you
measured for your coin and the binder or book?
Q3:Draw
a free body diagram for the inclined plane and the coin. Choose
coordinate axes so that the normal force is +yhat and uphill
is +xhat. Identify and label the following forces on the coin:
Normal force (F_{N}), Friction (F_{s} = m_{k}F_{N})and
Weight (W = mg).
Q4: Write
Newton's Second Law of Motion (N2) for any object in equilibrium.
What can we mathematically state about objects in equalibrium?
Is the coin in equalibrium at the Angle of Repose? Before and
After? Explain.
Q5: We
will use N2x and N2y. What calculations must be done to the three
forces you have drawn? Which forces do not require such calculations?
Q6: Write
component expressions for N2x and N2y. What do they mean (in words)?
Q7: Solve
for F_{N} and f_{s} alone. What do these expressions
mean (in words)?
Q8: Calculate
the division N2x/N2y. Using the identity: tan q
= (sin q) / (cos
q) to simplify your answer. What does this mean about the
role of an object's mass with regard to the Angle of Repose and
the coefficient of static friction? What are the units of static
friction? Does this make sense? Why?
Q9: What
do you calculate as your coefficent of static friction for the
binder and coin?
