Topic 6: deformation of solids

Question 1

state Hooke’s law

Answer 1

for a material that obeys Hooke’s law, its extension is directly proportional to the force exerted on it up to the limit of proportionality.

Question 2

when does an object reach its elastic limit

Answer 2

right after the limit of proportionality

Question 3

what is elastic deformation

Answer 3

before elastic limit, the object will return to its original shape after a load is removed.

Question 4

what is plastic deformation

Answer 4

after elastic limit, the object will not return to its original shape after a load is removed.

Question 5

what is the equation for spring constant

Answer 5

spring constant = force ÷ extension

Question 6

what are the units for spring costant

Answer 6

Nm^-1

Question 7

what is the equation for elastic energy (and work done) including force

Answer 7

W = Ep = ½Fx

Question 8

What is the derived equation from W = Ep = ½Fx

Answer 8

W = Ep = ½kx^2

Question 9

how do you find the work done from a force-extension graph

Answer 9

the area under the graph

Question 10

what is the spring constant of 2 springs in series

Answer 10

k = F ÷ 2x

Question 11

what is the spring constant of 2 springs in parallel

Answer 11

k = 2F ÷ x

Question 12

define stress

Answer 12

force per unit area (cross-sectional area)

Question 13

what is the equation for stress

Answer 13

stress = force ÷ area

Question 14

what are the units for stress

Answer 14

Nm^-2 or Pa

Question 15

what is the symbol for stress

Answer 15

sigma, σ

Question 16

what is tensile stress

Answer 16

a stretch

Question 17

what is compressive stress

Answer 17

a squash

Question 18

define strain

Answer 18

extension (or compression) per unit length

Question 19

what is the equation for strain

Answer 19

strain = extension ÷ original length

Question 20

what is the symbol for strain

Answer 20

ε

Question 21

define young modulus

Answer 21

the ratio of stress and strain

Question 22

explain young modulus

Answer 22

how stiff a material is, the measure of the ability of a material to withstand changes in length with an added load.

Question 23

what is the word equation for young modulus

Answer 23

young modulus = stress ÷ strain

Question 24

what is the symbol equation for young modulus

Answer 24

E = FL ÷ Ax

Question 25

What is the symbol for young modulus

Answer 25

E

Question 26

What are the units for young modulus

Answer 26

Nm^-2

Question 27

what can you interpret from a force extension graph within the elastic limit

Answer 27

the elastic potential energy is the area under the graph