Question 1

A design project requires you to construct a crane to lift a maximum load of 5000 kg and with a maximum upward acceleration of 2 m/s2. What size diameter steel cable should you use if the cable is to have a safety factor of 5?

Accepted Answer

A)  1.64 cm 
B)  1.10 cm 
C)  2.68 cm 
D)  3.00 cm 
E)  1.20 cm

Question 2

A planet has mass mP and radius RP. Suppose a rod of uniform diameter and length RP extends vertically from the surface of the planet. Where is the center of gravity of the rod as measured from the surface of the planet? The mass of the rod is much less than the mass of the planet.

Accepted Answer

A)  0 
B)  RP/3 
C)  2RP/5 
D)  RP/2 
E)  3RP/4

Question 3

A body is in translational equilibrium when

Accepted Answer

A)  it is acted on by a constant force. 
B)  no friction forces are involved. 
C)  it has a constant acceleration. 
D)  it has a constant velocity. 
E)  no contact forces are involved.

Question 4

A 10-m long plank (of negligible mass) is supported at each end by vertical cables. A person of unknown weight sits on the plank between the cables. The tension in the left cable is 300 N, and in the right cable it is 200 N. How far is the person sitting from the left cable?

Accepted Answer

A)  2.0 m 
B)  3.0 m 
C)  4.0 m 
D)  6.0 m 
E)  7.0 m

Question 5

Use the picture on the right to answer the next question.
A steel wire and an aluminum wire of the same length L and diameter d are joined to form a wire of length 2L. The wire is fastened to the ceiling and a mass m is attached to the other end. 
-The stress in the aluminum portion is ____ the steel portion.

Accepted Answer

A)  less than 
B)  equal to 
C)  greater than 
D)  depends on how tight m is attached to the steel 
E)  unable to tell

Exam 12: Static Equilibrium and Elasticity

A design project requires you to construct a crane to lift a maximum load of 5000 kg and with a maximum upward acceleration of 2 m/s². What size diameter steel cable should you use if the cable is to have a safety factor of 5?

A planet has mass m_P and radius R_P. Suppose a rod of uniform diameter and length R_P extends vertically from the surface of the planet. Where is the center of gravity of the rod as measured from the surface of the planet? The mass of the rod is much less than the mass of the planet.

A body is in translational equilibrium when

A 10-m long plank (of negligible mass) is supported at each end by vertical cables. A person of unknown weight sits on the plank between the cables. The tension in the left cable is 300 N, and in the right cable it is 200 N. How far is the person sitting from the left cable?