Two identical blocks are pulled along a rough surface as suggested in the figure. Which one of the following statements is false? The coefficient of kinetic friction is the same in each case. The normal force exerted on the O blocks by the surface is the same for both blocks. A force of the same magnitude is needed to keep each block moving. A force of the same magnitude was required to start each block moving. The magnitude of the force of kinetic friction is greater for the block on the right.

b) The elastic limit for some materials is difficult to determine exactly and so a yield point is defined as the point where a permanent deformation of 0.2% of the original length is obtained. Sketch a graph of stress against strain to illustrate this, marking appropriate points for the proportional limit, elastic limit and yield point.

Define the term work of force?

Yield strength, ultimate tensile strength, linear coefficient of thermal expansion, modulus of elasticity (E), proportional limit, and rupture strength are all examples of mechanical properties of engineering materials. O True False A non-destructive test is any examination of an object in any manner which will not impair the future usefulness of the object. Non-destructive tests include: magnetic-particle, impacting testing, radiography, eddy current, and fluorescent-penetrant. O True O False One way to make a metal stronger is to increase the metal's grain size. O True O False --- OL T A metal that has a crystalline structure is called amorphous. O True O False

Stress and strain: What are they and why are they used instead of load and deformation?

Give an example of Generalized Hooke’s Law?

Describe the historical development of the mechanics of materials?

2. Refer to the figure below. In addition to the load at point D, if another load Q (Q=10F) along x direction acts at the center of the right end section of bar OABC, solve for the maximum load F with a safety factor of 2.0 using the maximum shear stress theory. Find the stresses at the origin point O. Assume the yield strength of the steel is 42 kpsi with v=0.3. Hints: The centroid of a semicircle lies at a distance of 4r/(3) measured along the vertical radius (r) or y-direction. 2 in. 1-in D. -in R. 1-in D. 12 in 15 in 1-in D.

engineering stress, o CO b) Offset (x) 1. Which material has the highest yield strength? 2. Which material has the highest ultimate tensile strength? 3. Which material has the lowest tensile modulus (aka Young's modulus)? 4. Which material has the highest toughness? c) engineering strain, & 5. What offset (x) in engineering strain () should be used to calculate the yield strength? a. 2 b. 0.2 c. 0.02 d. 0.002 e. 0.0002

What are the tensile forces?