Define density.
Mass per unit volume
Density is a measure of how much mass is contained in a given volume.
What is the unit of density?
Kilogram per cubic metre (kg/m³)
This unit is used to express the density of substances.
How is the density of a substance calculated?
Density = mass/volume
This formula can be rearranged to find mass or volume as needed.
What is the volume of a cylinder?
Volume = π x r² x h
Where r is the radius and h is the height of the cylinder.
What is the relationship between gases, liquids, and solids in terms of density?
Gases have much lower density than liquids or solids
This is due to the average separation between molecules in different states of matter.
What is the first step to measure the density of a regular solid?
Measure its mass using a top pan balance
This is essential for calculating density.
What is the procedure to measure the density of a liquid?
- Measure mass of empty measuring cylinder
- Measure volume of liquid directly
- Calculate density from mass/volume
Using as much liquid as possible reduces percentage error.
What is the procedure to measure the density of an irregular solid?
- Measure the mass of the object
- Immerse in liquid and measure the increase in liquid level
The increase in liquid level equals the volume of the object.
What does Hooke’s law state about the force needed to stretch a spring?
The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length
This law was discovered by Robert Hooke, a seventeenth-century scientist.
In the equation F = kΔL, what does k represent?
The spring constant
The unit of k is N m⁻¹, and a greater value of k indicates a stiffer spring.
True or false: A spring will regain its initial length after being stretched beyond its elastic limit.
FALSE
If a spring is stretched beyond its elastic limit, it does not return to its original length when the force is removed.
What type of graph is produced when plotting tension against extension for a spring?
A straight line of gradient k through the origin
This graph illustrates the proportional relationship defined by Hooke’s law.
What is the unit of measurement for the spring constant?
N m⁻¹
This unit indicates the stiffness of the spring.
What happens to a spring when it is stretched beyond its elastic limit?
It does not regain its initial length
This indicates a permanent deformation of the spring.
What is the unit of stress in a wire under tension?
Pascal (Pa)
The unit of stress is equal to 1 Nm².
The tensile stress in a wire is calculated using the formula _______.
T/A
Where T is the tension and A is the area of cross section.
The tensile strain in a wire is defined as _______.
ΔL/L
Where ΔL is the extension (increase in length) of the wire.
True or false: Strain has a unit.
FALSE
Strain is a ratio and therefore has no unit.
What does the Young modulus relate to?
Stress and strain
It describes the relationship between tensile stress and tensile strain in materials.
The extension of a wire under tension can be measured using _______.
Scarl’s apparatus
This apparatus allows for precise measurement of extension under varying tension.
The extension of a wire is always measured from the _______.
Original (unstretched) length
This is crucial for accurate measurements.
What is the relationship between stress and force?
Stress is force per unit area
This relationship helps in understanding material behavior under load.
What is the Young modulus of a material?
The constant value of stress/strain
It is defined from the proportional relationship between tensile stress and tensile strain up to the limit of proportionality.
What is the ultimate tensile stress (UTS) of a material?
Its maximum tensile stress
UTS indicates the strength of a material before failure.
