Materials

Question 1

What is density ?

Answer 1

The mass per unit volume measured in kg/m^3

Question 2

What does the density of a material determine ?

Answer 2

It determines whether the object would float or sink.

Question 3

How would you convert from kgm^-3 to gcm^-3 ?

Answer 3

10^3 / 10^6 = 10 ^-3

Question 4

How would you find the density of regular and irregular objects ?

Answer 4

• using a measuring cylinder and measuring the volume increase or a eureka can
  -for regular objects can be found using the mass over volume

Question 5

How to calculate the density of alloys ?

Answer 5

( Mass x + mass y ) / volume

(Density*volume x ) + (density * volume y ) / volume

Question 6

What is an elastic material ?

Answer 6

A material which returns to its original shape after the deforming force is removed

Question 7

What is an inelastic material ?

Answer 7

An object that doesn’t return to it’s original once the deforming forces are removed

Question 8

What does hooked law state ?

Answer 8

The extension of a material is directly proportional to the force applied until the limit of proportionality

Question 9

What is the spring constant ?

Answer 9

A constant value measured in n/m (gradient of a force extension graph )

Question 10

What does the greater value for k tell us about the force required to produce an extension

Answer 10

The greater the value is the greater force is required to produce an extension

Question 11

What is the limit of proportionality

Answer 11

The point beyond with force and extension are no longer directly proportional ( hooked law is obey )

Question 12

What is the elastic limit ?

Answer 12

The point beyond the which the material is permanently deformed and does not return to its original length

Question 13

What is the breaking point ?

Answer 13

If the force is increased till a point where the atoms are broken apart (maximum force or stress before the material breaks )

Question 14

What is the ultimate tensile strength ?

Answer 14

The greatest possible applied force. All deformation beyond here the material would start to neck

Question 15

What is elastic strain energy ?

Answer 15

The energy stored within the material is stretched. Before the material reaches its elastic limit all the energy is stored as elastic strain energy.

Question 16

How can the work done or elastic strain energy be found using a force- extension graph ?

Answer 16

The area under the graph

Question 17

What would the force exerted on spring in series be ?

Answer 17

The force exerted would be the same

Question 18

What would the extension of the two springs in series be ?

Answer 18

The sum of the extensions

Question 19

How would you work out the total spring constant for spring in series ?

Answer 19

1/kt =1/k1 + 1/ K2 …

Question 20

What would happen to the extension for springs in parallel ?

Answer 20

It would be the same for each spring

Question 21

What would the force be for spring in a series circuit ?

Answer 21

The total force would be equal to the sum of the deforming forces exerted on each spring

Question 22

What is the spring constant for spring in parallel

Answer 22

Kt = k1 +k2 …

Question 23

What happens to the unloading line when an object passes the elastic limit ?

Answer 23

The unloading line would be parallel to the loading line

Question 24

From a force extension graph how would you be able to work out the work done to permanently deform the material ?

Answer 24

The area between the loading and unloading lines

Question 25

What is a tensile stress ?

Answer 25

Force exerted per unit cross sectional area , similar to pressure

Question 26

What is tensile strain ?

Answer 26

The ratio of the extension to the original length (change in length/ original length)

Question 27

What is the Young’s modulus ?

Answer 27

The ratio of tensile stress / tensile strain

E= Fl /A * change in length