PLTW-2.3.1 - STRESS & STRAIN CALCULATIONS

A weight of 18,000 lb is supported on a rectangular baseplate that is 9-in. wide and 2-ft long. The baseplate rests on a concrete slab. Determine the stress that the baseplate exerts on the concrete slab. Express your answer in units of psi.

• 83.3 psi

• 85.4 psi

• 166.7 psi

• 170.1 psi

A ¼-in. diameter rod must be machined on a lathe to a smaller diameter for use as a specimen in a tension test. The rod material is expected to break at a normal stress of 63,750 psi. If the tensile testing machine can apply no more than 925 lb of force to the specimen, calculate the maximum rod diameter that should be used for the specimen.

• 0.136 in

• 0.0046 in

• 0.068 in

• 0.0145 in

Determine the maximum load that a 0.50-in. diameter steel rod can support if the normal stress in the rod must not exceed 24,000 psi.

• 18,849.6 lbs

• 4712.4 lbs

• 122,231 lbs

• 4938.2 lbs

A 100-ft long steel wire has a cross-sectional area of 0.0144 in.². When a force of 270 lb is applied to the wire, its length increases by 0.75 in. Determine the Modulus of Elasticity.

• 3 x 10⁷ psi

• 18,750 psi

• 2.5 x 10⁶ psi

• 16,750 psi

A 1.25 in. by 3 in. rectangular steel bar is used as a diagonal tension member in a bridge truss. The diagonal member is 20 ft long, and its modulus of elasticity is 30,000,000 psi. If the strain in the diagonal member is measured as 0.001200 in./in., determine the total elongation of the bar.

• 0.33 in

• 0.29 in

• 1.25 in

• 0.42 in

Two 40-ft long wires made of differing materials are supported from the ceiling of a testing laboratory. Wire 1 is made of material H and has a diameter of 3/8 in. Wire 2 is made of material K and has a diameter of 3/16 in. When a load of 225 lb is applied to its lower end, wire 1 stretches 0.10 in. When the same 225 lb load is applied to the lower end of wire 2, wire 2 stretches 0.25 in. Compare materials H and K. Determine the modulus of elasticity of both materials. Which is the stiffer material?

• E_H = 9.8 x 10⁷ psi

  E_K = 1.6 x 10⁷ psi

  Material K is stiffer.

• E_H = 1.6 x 10⁷ psi

  E_K = 9.8 x 10⁷ psi

  Material K is stiffer.

• E_H = 9.8 x 10⁷ psi

  E_K = 1.6 x 10⁷ psi

  Material H is stiffer.

• E_H = 1.6 x 10⁷ psi

  E_K = 9.8 x 10⁷ psi

  Material H is stiffer.

A solid circular titanium control rod at 7,000 lb axial tension force where stress must not exceed 42,000 psi. Assume that the modulus of elasticity of the titanium is 16,500,000 psi and that the rod must elongate no more than 0.20 in. Determine the minimum rod diameter.

• 0.46 in

• 0.21 in

• 0.17 in

• 0.23 in

Which of Newton's laws is illustrated when a magician pulls a tablecloth out from under the dishes without disturbing them?

• first
• second
• third 
• fourth

Tags

NGSS.MS-PS2-1

Which of Newton's laws is represented when a person is pushed forward into their seatbelt when a car stops?

• 1st

• 2nd

• 4th

• 3rd

Which of Newton's laws explains why when you put a book on a table the table pushes on the book

• 3rd law

• 4th law

• 1st law

• 2nd law