Conceptual Multiple choices questions
5- Torque and Equilibrium
1. A 1-kg rock is suspended by a massless string from the left end of a 1.0 m
measuring stick. What is the mass of the measuring stick if it is balance by a support
force at the 0.25 m mark, as shown
a. 0.25 kg
b. 0.5 kg
c. 1.0 kg
d. 2.0 kg
e. 4.0 kg
2. If the net torque on an object is zero about a certain point,
a. it is not zero about any other point.
b. it is zero about only one other point.
c. it is zero about some other points.
d. it is zero about all other points.
e. the object must be in equilibrium.
3. When an object is in equilibrium, the axis about which torques are computed
a. must pass through one end of the object.
b. must pass through the center of mass of the object.
c. must intersect the line of action of at least one force acting on the object.
d. must be parallel with the line of action of at least one force acting on the
e. may be located anywhere.
4. A force F is exerted on the top right corner of a rectangular plate at an angle 60
above the horizontal, as shown below. The magnitude of the torque of the force F
about point A, the lower left corner is given by:
a. Fx sin 60o
b. Fy cos 60 o
c. Fr sin 60o o
d. Fx sin 60 + Fy cos 60
e. Fx cos 60 + Fy sin 60 o
5. A 5 N force acts on a 2 m radius uniform rotating circular platform. The force acts at
the edge of the platform and is directed at 30 to the outward radial direction. The
applied torque is:
a. 10 Nm
b. 8.7 Nm
c. 5 Nm
d. 2.5 Nm
e. 0 6. A 1.73 kg trophy is held at arm’s length, 63.7 cm from the shoulder joint. What
torque does the trophy exert about the shoulder if the arm is horizontal?
a. 21.6 Nm
b. 17.8 Nm
c. 10.8 Nm
d. 5.50 Nm
7. What torque does the trophy exert about the shoulder if the arm in previous problem
is at an angle of 24.5 below the horizontal?
a. 19.6 Nm
b. 16.7 Nm
c. 13.7 Nm
d. 9.83 Nm
e. 4.90 Nm
8. Figure below shows a rod of 2.0 m long that has two weights of 10 N and 30 N at its
ends. Assume the weight of the rod is negligible. At what point should the rod be
picked up that it stays at equilibrium, without rotating (Where is the balance point of
this rod?) Give your answer
respect to the left end.
a. 0.1 m
b. 0.3 m
c. 0.5 m
d. 1.0 m
e. 1.5 m
9. How much force you will exert on the rod of previous problem to hold it balance?
a. 0 N
b. 10 N
c. 30 N
d. 40 N
e. 100 N
10.A steel rod 2.00 m long is used as a lever to lift up one end of a 500 kg crate. If a
downward force of 350 N is exerted on one end of the rod, where should a block of
wood placed to act as the fulcrum? (Hint: Since only one end of the crate is lifted,
only half of its