6) materials

Question 1

state hookes law?

Answer 1

the extension of a spring is directly proportional to the force applied providing the limit of proportionality is not exceeded

Question 2

what is the formula for force that includes extension?

Answer 2

F=kx

Question 3

what does the force constant measure?

Answer 3

the stiffness of a spring

Question 4

what is elastic deformation?

Answer 4

once force is removed, it goes back to original length

Question 5

what is plastic deformation?

Answer 5

once force is removed, there is permanent structural damage so doesn’t go back to original length

Question 6

what is the elastic limit?

Answer 6

elastic limit is maximum extension for which plastic deformation does not occur

Question 7

what shows the work done on a force extension graph?

Answer 7

the area under the graph

Question 8

what is formula for work done?

Answer 8

0.5 x force x extension
or
0.5 x K x (extension)^2

Question 9

explain an experiment for hooke’s law?

Answer 9

1- attach spring with boss and clamp to a bench using g clamp
2- set up a meter ruler with resolution 1mm close to
spring
3- suspend slotted masses from spring and as u
measure each one, measure new total mass and
height
4- gradient equal force constant and will be directly
proportional
5- evaluation: measure mass with digital scale, 6 readings
then average for most accurate result

Question 10

what is the relationship between energy and extension?

Answer 10

energy is directly proportional to extension^2

Question 11

what does a force extension graph for rubber show?

Answer 11

does not obey hookes law
elastic deformation
more work done is needed to extend it then return it

Question 12

what does a force extension graph for polythene show?

Answer 12

doesn’t obey hookes law
more work is done to extend it
plastic deformation

Question 13

what is the formula for tensile stress?

Answer 13

force/ cross sectional area

Question 14

what is the formula for tensile strain?

Answer 14

extension/original length

Question 15

what is the formula for young modulus?

Answer 15

tensile stress /tensile strain

Question 16

what is the young modulus of a stress- strain graph?

Answer 16

the gradient of the linear section

Question 17

`what is the relationship between tensile stress of material and strength?

Answer 17

the larger the tensile stress the stronger the material

Question 18

determining young modulus of the wire experiment?

Answer 18

attach a 2m wire on one end over a pulley, wear eye protection in case wire snaps. measure diameter of wire using micrometre, record multiple values then take an average. area= pi x diameter^2 / 4. force is measured by mass x gravity. after adding mass, measure extension of wire with ruler.

Question 19

what occurs to the spring constant when two identical springs are attached in series and why?

Answer 19

it halves, as the force remains same but as two springs extension doubles. force= k x extension

Question 20

What is a brittle material?

Answer 20

A material that show only elastic behavior up to its breaking point, without plastically deforming.

Question 21

What is a polymeric material?

Answer 21

A material made from long chain molecules.

Question 22

what is a ductile material?

Answer 22

A material which can be drawn into a wire or hammered into thin sheets.

Question 23

What is the yield point of a material?

Answer 23

The point at which the material starts to extend rapidly as stress increases.

Question 24

What is the ultimate tensile strength of a material?

Answer 24

The maximum stress a material can withstand before breaking.

Question 25

When does the Young Modulus apply to a material?

Answer 25

When stress is proportional to strain OR when it is obeying Hooke’s law

Question 26

What is a tensile force?

Answer 26

A force produces an extension of the object.

Question 27

What is a compressive force?

Answer 27

A force that reduces the length of an object.