1) In Example problem 12-2, what would the magnitude of the force of elbow be if the mass of the weight was 7.00 kg?
570.7 N
649.2 N
698.1 N
465.4 N
2) The author points out in the CHECK portion of 12-4, that the answer makes sense because if h = R
Fmin ? zero
Fmin ? infinity
Fmin ? mass of the wheel
Fmin ? mass of the step
3) Refer to Figure 12-3 in Example 12-1. What point(s) can we say the net torque on the plank is zero?
The net torque is zero only about the right end.
The net torque is zero only about the left end.
The net torque is zero only about the right support.
The net torque is zero only about the left support.
The net torque is zero only about the center of mass.
The net torque is zero about all points.
4) When calculating the effect of the force due to gravity on a large extended object, you can act as if the force is applied directly to the object's...
angular center.
rotational center.
center of gravity.
center of rotational circumference.
5) In order for an object to be in static equilibrium...
the net force in all directions must be zero.
the net torque must be zero.
the object’s velocity must be zero.
(a) and (b).
All of the above.
6) As pointed out in the CHECK portion of 12-2, we can check our answer by
noting the magnitude of the force in the elbow is less than the weight of object.
noting that the torques only sum to be zero when summed about the elbow.
by summing the torques about a different point.
by noting the when the length of the forearm ? 0, the force of the elbow ? infinity.
7) The units for Young's modulus are
force (e.g. Newtons)
unitless (e.g. cm/cm)
force times length (e.g. foot-pounds)
force per area (e.g. pounds per square inch)
8) In Example 12-6, about what point does the author sum the torques on the ladder?
The center of gravity.
The lower end.
The upper end.
We can not tell what point he sums them about.
9) An object is hanging motionless by a string. We know that the location of its center of gravity is
zero.
negative.
positive.
directly below the suspension point.
directly above the suspension point.
equal to the cross product of its moment arm and tension in the string.
10) If an object acted on by three forces is in static equilibrium, what can we say about the lines of action?
They all intersect at the same point
They are all parallel.
They are all perpendicular.
They are all zero.