Density is the mass per unit volume of an object.

If mass is measured in grams and volume in cm 3 , then density is measured in .......... .

If mass is measured in grams and volume in cm 3 , then density is measured in g/cm 3 .

When converting a larger unit to a smaller unit, do you multiply or divide by the conversion factor?

You multiply (×) by the conversion factor, for example 125 m = 125 × 100 = 12 500 cm.

When converting a smaller unit to a larger unit, do you multiply or divide by the conversion factor?

You divide (÷) by the conversion factor, for example 5 g = 5 ÷ 1000 = 0.005 kg.

How should the conversion factor be adjusted when converting squared or cubic units, such as mm 3 to m 3 ?

The conversion factor must also be squared or cubed , for example 1 cm 3 = 1 ÷ (100) 3 = 1 x 10 -6 m 3 .

True or False? A balloon occupying a larger volume than a small bar of lead means the balloon must be denser.

False. Density depends on mass per unit volume , not volume alone; the balloon is less dense than the lead despite occupying a larger volume, because it has far less mass.

A material obeys Hooke's law if the extension is directly proportional to the applied force (load), up to the limit of proportionality .

Define the spring constant .

A property of a material that measures its stiffness ; the larger the spring constant, the stiffer the material.

How is extension defined?

Extension = stretched length − unstretched length.

On an extension-force graph (with extension on the y-axis and force on the x-axis), the gradient is equal to .......... .

On an extension-force graph (with extension on the y-axis and force on the x-axis), the gradient is equal to 1/*k *.

True or False? The limit of proportionality and the elastic limit occur at the same point on a force-extension graph.

False. They are different points: beyond the limit of proportionality , extension is no longer proportional to force; beyond the (later) elastic limit , the material no longer returns to its original length.

Define ultimate tensile stress .

The maximum force per original cross-sectional area a wire can support before it breaks.

Tensile strain is dimensionless because it is the ratio of .......... .

Tensile strain is dimensionless because it is the ratio of lengths .

Define yield stress .

The stress at which a material extends plastically for no or a small increase in stress.

Define breaking stress .

The maximum stress a material can withstand before it fractures.

On a stress-strain graph, what does the area under the Hooke's law (straight-line) region represent?

The elastic strain energy stored per unit volume .

True or False? In the plastic region of a stress-strain graph, a material returns to its original shape once the applied force is removed.

False. In the plastic region , the material has deformed permanently and will not return to its original shape when the force is removed; this only happens in the elastic region .

What is the elastic strain energy (work done stretching a material) equal to, on a force-extension graph?

The area under the force-extension graph .

A material with a high breaking stress is considered .......... , meaning it can stretch a long way before breaking.

A material with a high breaking stress is considered ductile , meaning it can stretch a long way before breaking.

Define ultimate tensile stress (UTS) .

The maximum stress that a material can withstand.

At position A, the highest point of a mass oscillating vertically on a spring, what are its kinetic energy and gravitational potential energy?

Kinetic energy is zero (stationary) and gravitational potential energy is at a maximum .

At position C, the lowest point of a mass oscillating vertically on a spring, what are its elastic potential energy and gravitational potential energy?

Elastic potential energy is at a maximum (maximum extension) and gravitational potential energy is at a minimum .

True or False? For a horizontal mass-spring system, gravitational potential energy must be considered along with kinetic and elastic potential energy.

False. For a horizontal mass-spring system there is no gravitational potential energy to consider; the energy only converts between kinetic and elastic potential energy.

Define elastic deformation .

When the load is removed, the object returns to its original shape .

Define plastic deformation .

When the load is removed, the object does not return to its original shape or length; it is permanently deformed.

How can the elastic and plastic regions be identified on a force-extension graph?

The elastic region is a straight line, where extension is proportional to force. The plastic region is where the graph starts to curve , and extension is no longer proportional to force.

Define brittle materials , giving two examples.

Materials with very little or no plastic region; they break with little elastic and insignificant plastic deformation. Examples: glass and concrete .

Define ductile materials , giving two examples.

Materials with a larger plastic region that stretch into a new shape before breaking. Examples: rubber and copper .

On a stress-strain or force-extension graph, a brittle material is represented by a straight line through the origin with .......... .

On a stress-strain or force-extension graph, a brittle material is represented by a straight line through the origin with no or negligible curved region .

True or False? Plastic deformation should be described as the material "not obeying Hooke's law".

False. Although mostly correct, plastic deformation should be described as the material being permanently deformed , rather than simply "not obeying Hooke's law".

For a metal wire stretched beyond its limit of proportionality, what does the area between the loading and unloading lines on a force-extension graph represent?

The work done to permanently deform the wire.

Why does the unloading line for a plastically deformed metal wire not pass through the origin?

Because the wire is permanently extended , so it is not at zero extension when the force is removed.

On a rubber band's force-extension graph, what do areas X and Y represent?

Area X is the work done heating the rubber (increase in thermal energy). Area Y is the work done by the rubber when it returns to its original shape.

A rubber band becomes warm when stretched and contracted because some energy is transferred to .......... .

A rubber band becomes warm when stretched and contracted because some energy is transferred to heat (thermal) energy .

What is the role of shock absorbers in a vehicle's suspension system?

They dampen the compression and rebound of the springs, converting kinetic energy into thermal energy , which is dissipated, keeping the tyres on the road.

What happens to the resistance provided by a shock absorber as the springs in the suspension move faster, for example when hitting a bump at high velocity?

The shock absorber provides more resistance .

True or False? Since a rubber band returns to its original length with no permanent extension, no energy is lost when it is stretched and released.

False. Although the rubber band is elastic (no permanent extension), the curve for contraction lies below the curve for stretching; the difference in strain energy is transferred to thermal energy as the rubber warms up.

A LevelPhysicsAQAFlashcardsMechanics & MaterialsBulk Properties of Solids

Bulk Properties of Solids (AQA A Level Physics): Flashcards

Exam code: 7408

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Cards in this collection (44)

Define density.
Density is the mass per unit volume of an object.
What is the equation for density in terms of mass and volume?
$density = \frac{mass}{volume}$
If mass is measured in grams and volume in cm³, then density is measured in ...........
If mass is measured in grams and volume in cm³, then density is measured in g/cm³.
When converting a larger unit to a smaller unit, do you multiply or divide by the conversion factor?
You multiply (×) by the conversion factor, for example 125 m = 125 × 100 = 12 500 cm.
When converting a smaller unit to a larger unit, do you multiply or divide by the conversion factor?
You divide (÷) by the conversion factor, for example 5 g = 5 ÷ 1000 = 0.005 kg.
How should the conversion factor be adjusted when converting squared or cubic units, such as mm³ to m³?
The conversion factor must also be squared or cubed, for example 1 cm³ = 1 ÷ (100)³ = 1 x 10^-6 m³.
True or False?
A balloon occupying a larger volume than a small bar of lead means the balloon must be denser.
False.
Density depends on mass per unit volume, not volume alone; the balloon is less dense than the lead despite occupying a larger volume, because it has far less mass.
Define Hooke's law.
A material obeys Hooke's law if the extension is directly proportional to the applied force (load), up to the limit of proportionality.
What is the equation for Hooke's law?
$F = k Δ L$
Where F is force (N), k is the spring constant (N m^-1), and ΔL is extension (m).
Define the spring constant.
A property of a material that measures its stiffness; the larger the spring constant, the stiffer the material.
How is extension defined?
Extension = stretched length − unstretched length.
What does the gradient of a force-extension graph represent, in the region where Hooke's law is obeyed?
The spring constant, k.
On an extension-force graph (with extension on the y-axis and force on the x-axis), the gradient is equal to ...........
On an extension-force graph (with extension on the y-axis and force on the x-axis), the gradient is equal to 1/*k*.
True or False?
The limit of proportionality and the elastic limit occur at the same point on a force-extension graph.
False.
They are different points: beyond the limit of proportionality, extension is no longer proportional to force; beyond the (later) elastic limit, the material no longer returns to its original length.
Define tensile stress.
Tensile stress (σ) is the force exerted per unit cross-sectional area of a material.
$σ = \frac{F}{A}$
Measured in pascals (Pa).
Define tensile strain.
Tensile strain is the extension per unit length.
$strain = \frac{Δ L}{L}$
Strain is dimensionless (no units), though it is sometimes expressed as a percentage.
Define ultimate tensile stress.
The maximum force per original cross-sectional area a wire can support before it breaks.
Tensile strain is dimensionless because it is the ratio of ...........
Tensile strain is dimensionless because it is the ratio of lengths.
Define yield stress.
The stress at which a material extends plastically for no or a small increase in stress.
Define breaking stress.
The maximum stress a material can withstand before it fractures.
On a stress-strain graph, what does the area under the Hooke's law (straight-line) region represent?
The elastic strain energy stored per unit volume.
True or False?
In the plastic region of a stress-strain graph, a material returns to its original shape once the applied force is removed.
False.
In the plastic region, the material has deformed permanently and will not return to its original shape when the force is removed; this only happens in the elastic region.
What is the elastic strain energy (work done stretching a material) equal to, on a force-extension graph?
The area under the force-extension graph.
What is the equation for elastic strain energy in terms of average force and extension?
$E = \frac{1}{2} F Δ L$
What is the equation for elastic strain energy in terms of the spring constant and extension?
$E = \frac{1}{2} k {(Δ L)}^{2}$
A material with a high breaking stress is considered .........., meaning it can stretch a long way before breaking.
A material with a high breaking stress is considered ductile, meaning it can stretch a long way before breaking.
Define ultimate tensile stress (UTS).
The maximum stress that a material can withstand.
At position A, the highest point of a mass oscillating vertically on a spring, what are its kinetic energy and gravitational potential energy?
Kinetic energy is zero (stationary) and gravitational potential energy is at a maximum.
At position C, the lowest point of a mass oscillating vertically on a spring, what are its elastic potential energy and gravitational potential energy?
Elastic potential energy is at a maximum (maximum extension) and gravitational potential energy is at a minimum.
True or False?
For a horizontal mass-spring system, gravitational potential energy must be considered along with kinetic and elastic potential energy.
False.
For a horizontal mass-spring system there is no gravitational potential energy to consider; the energy only converts between kinetic and elastic potential energy.
Define elastic deformation.
When the load is removed, the object returns to its original shape.
Define plastic deformation.
When the load is removed, the object does not return to its original shape or length; it is permanently deformed.
How can the elastic and plastic regions be identified on a force-extension graph?
The elastic region is a straight line, where extension is proportional to force.
The plastic region is where the graph starts to curve, and extension is no longer proportional to force.
Define brittle materials, giving two examples.
Materials with very little or no plastic region; they break with little elastic and insignificant plastic deformation.
Examples: glass and concrete.
Define ductile materials, giving two examples.
Materials with a larger plastic region that stretch into a new shape before breaking.
Examples: rubber and copper.
On a stress-strain or force-extension graph, a brittle material is represented by a straight line through the origin with ...........
On a stress-strain or force-extension graph, a brittle material is represented by a straight line through the origin with no or negligible curved region.
True or False?
Plastic deformation should be described as the material "not obeying Hooke's law".
False.
Although mostly correct, plastic deformation should be described as the material being permanently deformed, rather than simply "not obeying Hooke's law".
For a metal wire stretched beyond its limit of proportionality, what does the area between the loading and unloading lines on a force-extension graph represent?
The work done to permanently deform the wire.
Why does the unloading line for a plastically deformed metal wire not pass through the origin?
Because the wire is permanently extended, so it is not at zero extension when the force is removed.
On a rubber band's force-extension graph, what do areas X and Y represent?
Area X is the work done heating the rubber (increase in thermal energy).
Area Y is the work done by the rubber when it returns to its original shape.
A rubber band becomes warm when stretched and contracted because some energy is transferred to ...........
A rubber band becomes warm when stretched and contracted because some energy is transferred to heat (thermal) energy.
What is the role of shock absorbers in a vehicle's suspension system?
They dampen the compression and rebound of the springs, converting kinetic energy into thermal energy, which is dissipated, keeping the tyres on the road.
What happens to the resistance provided by a shock absorber as the springs in the suspension move faster, for example when hitting a bump at high velocity?
The shock absorber provides more resistance.
True or False?
Since a rubber band returns to its original length with no permanent extension, no energy is lost when it is stretched and released.
False.
Although the rubber band is elastic (no permanent extension), the curve for contraction lies below the curve for stretching; the difference in strain energy is transferred to thermal energy as the rubber warms up.

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