Phy 121L/131L
Pre-Lab: Static Equilibrium
Name:
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Choose the best answer. Refer to the lab manual for definitions of the variables used below.
(10 pts total)
1. What does the magnitude of torque (“turning force”) depend on?
[2 pts]
a. the “parallel” component of force, F║
b. the perpendicular component of force, F
c. the pivot point, O
d. the distance from the pivot point, d, that the force is applied
e. b and d are correct
f. a and c are correct
2. Under what condition(s) is an object said to be in static equilibrium?
a. its linear and angular acceleration are zero
b. the net force is zero
c. the net torque is zero
d. All of the above are conditions for static equilibrium.
e. None of the above are conditions for static equilibrium.
[2 pts]
3. According to the lab manual, what extended body will we use to investigate the balance of
forces and torques?
[1 pt]
a. wrench
b. meter stick
c. door
d. fulcrum
4. What makes a torque “positive” (note the ± sign in eqn. 1)?
[1 pt]
a. the torque causes a counterclockwise rotation about the pivot point
b. the torque causes a clockwise rotation about the pivot point
c. the point where the force is applied is to the left of the pivot point
d. the point where the force is applied is to the right of the pivot point
5. Approximately where would you expect the center of mass (CM) to be for a meter stick?[1 pt]
a. 0 cm
b. 25 cm
c. 50 cm
d. 75 cm
e. 100 cm
6. When considering whether an object is in static equilibrium, you must remember that the
weight of the object itself is a force that must be considered. The weight acts at the center of
mass of the object. If an object weighs 1.0 N and the pivot point is at the center of mass,
what is the torque on the object due to the weight?
[1 pt]
a. 1.0 Nm
b. 0 Nm
c. 9.8 Nm
d. There is not enough information.
7. See fig. 7 in your lab manual. If a force, F1 = 3.80 N is applied at 70.0 cm on a meter stick,
and the pivot is at 49.3 cm, what is the torque on the meter stick due to F1? [1 pt]
a. 3.80 Nm
b. 266 Nm
c. 2.66 cm
d. 78.7 Nm
e. 0.787 Nm
8. Three forces are applied to a meter stick in static equilibrium. When the pivot point is at “50
cm”, the torques are +21 Nm, -113 Nm, and +92 Nm. What is the net torque on the meter
stick when the pivot point is at “100 cm”?
[1 pt]
a. 0 Nm
b. 226 Nm
c. 42 Nm
d. There is not enough information.
CSU Pomona
3/25/05
Dr. Julie J. Nazareth