Properties of materials (12)

Question 1

Weight

Answer 1

the pull of gravity on an object. W=mg

Question 2

Compressive forces

Answer 2

are forces that tend to squeeze an object and reduce its size in the direction that the forces are applied.

Question 3

Tensile forces

Answer 3

are forces that act to pull or stretch an object.

Question 4

Spring constant, k

Answer 4

a measure of how hard it is to bend or stretch a spring. A large spring constant means that the spring is stiff. Units of Nm-1.

Question 5

Extension

Answer 5

is the length a material has stretched when a load is added. It is calculated by subtracting the original length of the material from the length when stretched.

Question 6

Limit of proportionality

Answer 6

is the endpoint of the linear section of a force-extension graph.

Question 7

Elastic limit

Answer 7

is the load above which a material is permanently deformed.

Question 8

Elastic (material)

Answer 8

a material is said to be elastic when it returns to its original dimensions once the applied load is removed.

Question 9

Plastic (material)

Answer 9

a material is said to be plastic when it is permanently deformed and does not return to its original dimensions once the applied load is removed.

Question 10

Ductility

Answer 10

ductile materials can be formed into wires by stretching them. They show ductility. Neck when fracturing.

Question 11

Brittle

Answer 11

a brittle material is one that shows little, or no, plastic deformation before breaking. Clean fracture.

Question 12

Elastic strain energy

Answer 12

is the energy stored by stretched materials.

Question 13

Tensile stress, σ

Answer 13

=force/(cross-sectional area) (units Nm-2)

Question 14

Tensile strain, ε

Answer 14

=extension/(original length) (unitless; sometimes expressed as percentage)

Question 15

Young Modulus, E

Answer 15

is a measure of the stiffness of an elastic material. It does not depend on the dimensions of the sample being tested. Measured in Pa or Nm-2. =stress/strain