Bulk properties of solids Flashcards – AQA A-level Physics (7408)

What equation expresses Hooke’s law for a spring in terms of applied force $F$, stiffness $k$ and extension $\Delta L$?

$F = k\Delta L$

What is a spring’s stiffness, and what is its unit?

The force per unit extension, measured in $\mathrm{N\,m^{-1}}$.

What does a larger spring constant mean for the force needed to produce the same extension?

A greater force is needed.

Where on a force–extension graph does the proportional relationship in Hooke’s law hold?

In the linear region.

How does deformation on unloading differ before and beyond the elastic limit?

Elastic deformation is reversible; beyond the elastic limit, some permanent deformation remains.

How do the limit of proportionality and the elastic limit differ?

A material can still deform elastically after force and extension cease to be proportional.

What is elastic strain energy?

Energy stored in an elastically deformed object that is recoverable when it returns to its original shape.

What represents the work done during extension on a force–extension graph?

The area under the graph.

What is the stored energy for a spring obeying Hooke’s law from zero extension to a final force $F$ and extension $\Delta L$?

$E=\frac{1}{2}F\Delta L$

Why is there a factor of one-half in the elastic strain energy formula for a spring obeying Hooke’s law from zero extension?

The area under its force–extension graph is triangular.

How does permanent deformation affect the energy recoverable from work done in deformation?

Not all the work done is recoverable as elastic strain energy.

What forms can energy released by a spring become?

Kinetic energy, gravitational potential energy, or a combination of both.

What is the equation for kinetic energy in terms of mass and speed?

$E_k = \frac{1}{2}mv^2$

What is the equation for the change in gravitational potential energy for a height change $\Delta h$?

$\Delta E_g = mg\Delta h$

What happens to energy transferred into permanent deformation or other non-recoverable forms?

It is unavailable for return as elastic energy.

How should an energy balance for deformation and motion account for non-recoverable transfers?

Compare initial and final energies while including energy transferred into non-recoverable forms.

What must happen to a vehicle’s kinetic energy in a collision?

It must be transferred to other energy stores or processes.

What role can deformation play in a collision, and what possible drawback accompanies it?

Deformation can absorb energy, but it may also damage structures.

What must transport designers balance against safety consequences?

Other impacts, such as resource use.

How does energy conservation help assess a transport design?

It helps assess what the design can achieve.

What does ethical evaluation consider in transport design?

Who benefits, who bears risks, and how competing consequences are weighed.