Materials

Question 1

What is the density of a material

Answer 1

The density of a material is it’s mass per unit volume

Question 2

State the equation used to calculate density

Answer 2

Density =mass/volume

Question 3

What is the unit of density?

Answer 3

Kgm^-3

Question 4

When an object is submerged in a fluid, what determines the upthrust it experiences

Answer 4

The upthrust of a submerged object is equal to the weight of the fluid displaced

Question 5

What determines whether an object floats or sinks

Answer 5

The balance between the weight and upthrust of the object. If the weight exceeds the upthrust, the object will sink

Question 6

Why will a uniform object with a density greater than that of a liquid it is submerged in always sink

Answer 6

-the upthrust of the object will be equal to the weight of the of the liquid displaced
-therefore there maximum upthrust will be equal to the density of the fluid x volume of object x gravitational field

Question 7

What shaped object does stokes’ law apply to?

Answer 7

Stokes’ law only applies to small spherical objects

Question 8

What type of flow is required for stokes’ law to apply?

Answer 8

Laminar

Question 9

What does stokes’ law allow you to calculate

Answer 9

The viscous drag force that a small spherical object experiences when falling at low speeds through a viscous fluid with laminar flow

Question 10

State the stokes’ law equation

Answer 10

F=6πnrv

n=viscosity
r=radius of sphere
v=speed of sphere

Question 11

What is elastic deformation

Answer 11

An object has undergone elastic deformation if it returns to its original shape once the deforming force is removed

Question 12

What is plastic deformation

Answer 12

An object has undergone plastic deformation of it no longer returns to its original shape once the deforming forces are removed. It will have permanent deformation

Question 13

Express hooke’s law in words

Answer 13

The extension of an elastic object is directly proportional to the force that is applied to it, up to its limit of proportionality

Question 14

What is the limit of proportionality

Answer 14

The point beyond which the force and extension will no longer be directly proportional to each other - hooke’s law is no longer obeyed

Question 15

What is the elastic limit

Answer 15

The point beyond which the object will no longer elastically deform, and will instead deform plasticslly

Question 16

State the defining equation of hooke’s law

Answer 16

F=kx

Question 17

What is mechanical stress

Answer 17

The force experienced by an object per unit area

Question 18

State the equation for stress

Answer 18

Stress=F/A

Question 19

What is the unit of stress

Answer 19

Nm^-1

Question 20

State the equation for strain

Answer 20

Strain=x/L

Question 21

What is the unit of strain

Answer 21

Strain is unitless

Question 22

What does the young modulus of a material tell you

Answer 22

A materials young modulus is a measure of how much force is required for a given extension, regardless of the objects dimensions

Question 23

What equation is used to calculate a materials young modulus

Answer 23

YM=stress/strain

Question 24

What unit is used for the young modulus of a material

Answer 24

Nm^-2

Question 25

What is breaking stress

Answer 25

Breaking stress is the maximum stress that an object can withstand before fracturing

Question 26

What is the yield point?

Answer 26

The point which the object will experience a large extension without substantial increase in the force applied

Question 27

What type of energy is stored in an object that has been stretched

Answer 27

Elastic potential energy

Question 28

State two equations used to calculate the energy stored in a spring

Answer 28

E=1/2 Fx
E=1/2 kx^2

Question 29

What does the gradient and area represent on a force-extension graph

Answer 29

-the gradient represents the elastic constant (k)
-the area represents the Aston potential energy stored in the spring