KCL Section 2: Solids (Materials) Flashcards
State three SI base units
m
kg
s
State 2 SI derived quantities
kgm^-1s^-1
kgms^-2
Define upthrust
The weight of the displaced fluid
Draw a free-body force diagram for a particle accelerating upwards through a fluid
^ I I Upthrust I O I Drag + weight ↓
Explain why a raindrop will reach a maximum velocity
Drag will equal weight
_____ - how difficult it is to scratch the surface
_____ - how much it deforms under large forces
_____ - how much energy from impacts it can absorb without breaking
_____ - how much it will shatter or crack when subjected to a shock
_____ - how much breaking stress it can withstand
_____ - how easily it can be formed into thin sheets
_____ - how easily it can be drawn into a wire
Do not use any of these terms unless you are confident you are using the correct term.
Hardness Stiffness Toughness Brittleness Strength Malleability Ductility
What did Hooke discover?
Hooke discovered that the extension of a stretched wire is directly proportional to the force acting on the wire.
ΔF = kΔx
where k is the force constant (stiffness of the wire).
Can this formula be used for objects that aren’t springs?
This formula can be applied to all solids, up to their limit of proportionality.
The limit of proportionality varies for different materials.
Describe Hooke’s law in words
Force is directly proportional to extension
Describe the difference between x and Δx
x is the length of the spring whereas Δx is the extension
Express a newton in SI base units
kgms^-2
Describe what the constant k represents
Spring constant
Describe what is meant by the limit of proportionality
A limit that when surpassed the object will no longer extend proportionally to the force exerted.
A 350 g mass is hung on a piece of wire. What force is acting on the wire?
A weight of 3.4N
A 13 N force is applied to a piece of metal (k = 120 Nm-1) fixed to a table. Calculate the expected extension of the metal.
0.1m
A 4.3 N force is applied to a piece of metal (k = 830 Nm^-1) fixed to a table. Calculate the expected extension of the metal.
0.0052m
A wire is 1.1 m long and has a force constant of 550 Nm^-1. Calculate the new length when a force of 9.2 N is applied.
1.117m
A spring has a stiffness constant of 50Nm^-1 and is 3.0 cm long naturally. How long would it be if a 200g mass were hung from it?
6.9cm
A 0.70 kg mass is attached to a spring. The spring extends by 84 cm. What is the force constant?
k = 8.175 Nm^-1
What is the magnitude of the force required to stretch a 20.0 cm long wire, with a force constant of 590 Nm-1, to a length of 21.0 cm?
F = 5.9 N
What is the force constant of a spring that needs a force of 3 N to be compressed from 40 cm to 35 cm?
k = 60 Nm^-1
A spring is extended by 11.5 cm and held in place with a force of 380 N. What is the force constant of the spring?
k = 3300 Nm^-1
A metal wire is extended to a length of 65.4 cm using a force 4030 N. The force constant of the material is 1280 Nm-1; what was the original length or the wire?
x = 0.623 m
