Suppose you're selecting materials for a frictional braking system which will be used to bring a moving body to a stop. It is imperative that you choose a braking surface material which will not thermally degrade as mechanical kinetic energy is converted to thermal energy during the braking process. You have a list of candidate materials for your braking system which includes maximum permissible average power dissipation. In order to relate average power dissipation rate to your system's mechanical properties (and select an appropriate material), what information will you need?

Which of the following statements is incorrect regarding the mechanical characteristics of polymers? (This question has only one correct answer) а. Metals typically have higher tensile strength but lower elastic modulus than polymers O b. The mechanical characteristics of polymers are much more sensitive to temperature changes near room temperature С. Elongation at break is typically greater for polymers than metals d. Decreasing the temperature results in increased brittleness in polymers

Which of the following are incorrect regarding the crystallinity and mechanical behavior of polymers? a. As temperature is reduced, necking behavior of plastic tensile bars completely disappears b. Semi-crystalline polymers are heat treated to increase crystallinity and improve strength c. Heat treatment always results in enhanced polymer strength, modulus, and brittleness d. Strain softening happens in elastomers where the deformation gradually leads to a decrease in stiffness under constant strain rate e. Increasing the degree of crystallinity generally increases polymer strength, elastic modulus, and ductility in semi-crystalline polymers f. The stress-strain curve slope for totally elastic and brittle polymers is always positive

Which statements are correct regarding the mechanical properties of polymers? a. Drawing increases alignment and strength, and decreases ductility (% elongation) b. Annealing increases alignment, strength and elastic modulus c. Increasing temperature results in increased elastic modulus and strength, and decreased elongation d. Decreasing strain rate causes decreased strength and elastic modulus and increased elongation e. A higher degree of crosslinking generally results in decreased percent elongation at break, and increases strength