Materials

Question 1

Equation for density

Answer 1

Density = Mass / Volume (density is mass per unit volume)

Question 2

Define Upthrust

Answer 2

Upthrust is the weight of fluid displaced

Question 3

How do you calculate upthrust?

Answer 3

Find the volume of fluid displaced Use W = mg to find the weight of fluid

Question 4

State Stoke’s Law and its conditions

Answer 4

F = 6πηrv where η is the vicosity of the fluid, r is the radius and v is the velocity It’s only valid for small spherical objects moving under laminar flow at low velocities

Question 5

Define Stiff

Answer 5

large force / load / stress for (small) extension

Question 6

Define Hooke’s Law

Answer 6

The force directly proportional to the extension

Question 7

Define Elastic Deformation

Answer 7

Returns to original shape when the deforming force is removed

Question 8

Define Plastic Deformation

Answer 8

Does not return to original shape when deforming force is removed - permanently deformed

Question 9

Define Elastic Limit

Answer 9

The point below which the material exhibits elastic deformation

Question 10

Define the limit of proportionality

Answer 10

Force proportional to extension up to this point

Question 11

Define Yield Point

Answer 11

yield point – point at which plastic deformation begins / point at which material shows a larger increase in strain for a smaller increase in stress (1)

Question 12

Give the formula for calculating elastic energy

Answer 12

E = 1/2kx^2 (Consider the area under a force extension graph)

Question 13

Draw a labelled force extension graph

Answer 13

Question 14

Give the equation for Young Modulus

Answer 14

Stress/Strain = F/A / Δx/x = Fx/AΔx

Question 15

Give the equation for stress

Answer 15

σ = F/A

Question 16

Give the equation for strain

Answer 16

ε = Δx/x

Question 17

Draw a stress-strain graph and explain what the gradient represents

Answer 17

The gradient is young modulus

Question 18

Give the equation for a transverse wave on a string

Answer 18

v = √(T/μ) where T is the tension in the string and the linear density of the string.

Question 19

Define Strength

Answer 19

Strength is the maximum force applied to a body before it breaks.

Question 20

Define Breaking Stress

Answer 20

The maximum stress that can be applied to an object before it breaks.