Hooke's Law: Force–Extension Relationships
- State and use Hooke's Law:
F = kxwithin the elastic limit. - Define and distinguish length and extension; identify units (N, m).
- Collect and graph experimental data; determine spring constant
kfrom gradient. - Identify the limit of proportionality and discuss elastic vs. plastic behavior.
- Apply concepts to real devices (trampoline, bungee, suspension) and safety.
- Use sentence frames to justify proportionality:
“When doubles, the
doubles (within the elastic limit).” - Define technical terms verbally and in writing with units (N, m, N·m−1).
- Interpret and describe graphs using slope/gradient language to obtain
k.
| English | Русский | Қазақша |
|---|---|---|
| Hooke's Law | Закон Гука | Гук заңы |
Force (F) | Сила (F) | Күш (F) |
Extension (x) | Удлинение (x) | Созылу (x) |
Spring constant (k) | Жёсткость пружины (k) | Серпімділік коэффициенті (k) |
| Elastic limit | Предел упругости | Серпімділік шегі |
| Limit of proportionality | Предел пропорциональности | Пропорционалдық шегі |
| Elastic / Plastic | Упругий / Пластический | Серпімді / Пластикалық |
| Gradient / Slope | Наклон / Уклон | Еңіс / Градиент |
| Restoring force | Восстанавливающая сила | Қалпына келтіретін күш |
| Work / Energy in spring | Работа / Энергия пружины | Серіппедегі жұмыс / Энергия |
Use ready-made flashcards to rehearse vocabulary (choose one):
Hooke's Law: within the elastic limit, the needed to stretch a spring is proportional to its , F = kx.
Spring constant (k): measure of stiffness; units N·m−1.
Limit of proportionality: point beyond which F is no longer proportional to x.
Elastic vs plastic: elastic objects return to original length after unloading; plastic objects do not.
Core idea. For small deformations, many materials behave approximately linearly: the restoring force is proportional to displacement from equilibrium. For an ideal spring: F = -kx, where x is extension (m), k is spring constant (N·m−1). The negative sign indicates the force opposes displacement. In the force–extension model used for lab work, we often write F = kx (magnitudes) up to the limit of proportionality. The slope of the linear region of an F-vs-x graph equals k. Elastic potential energy stored: E = (1/2) k x^2. Real materials deviate beyond the elastic limit where permanent (plastic) deformation occurs.
References suitable for background reading: OpenStax College Physics & University Physics (Hooke's Law), Save My Exams (CIE 9702 revision), BBC Bitesize.
- Easy: A spring extends
0.04 munder2 N. Findk. - Medium: A spring has
k = 200 N·m−1. What extension forF=6 N? What energy is stored? - Medium: Explain why the best-fit line should pass through the origin only within the elastic region; how would zero error affect the intercept?
- Challenging (critical thinking): Two springs in parallel support the same load. One has twice the
kof the other. Compare load sharing and discuss how this affects safety factors in suspension design.
- Match the term to its definition: Hooke's Law; extension; spring constant; elastic limit.
- Fill the gaps: “The is proportional to the
until the ______ of proportionality.” - True/False: A larger
kmeans a stiffer spring.
Alternative picks: Chad Physics — Springs & Elastic Potential Energy; BBC Bitesize explainer.
A spring extends 0.025\,m under a 1.5\,N load. Find k.
A 300\,N·m^{-1} spring stores 0.27\,J of energy. Find x.
Two identical springs in series each have k=200\,N·m^{-1}. Find the equivalent k_{eq}.
A mass 0.50\,kg hangs from a spring with k=80\,N·m^{-1}. Find small-oscillation period T.
Explore the simulation. Measure L_0, vary mass, record x, and test linearity.
Choose an online quiz for teamwork (teacher projects; students discuss before voting):
- A spring with
k=150\,N·m^{-1}is stretched by a3.0\,Nforce. Findx. Comment on whether this likely lies in the elastic region. - A spring obeys
F=kxup tox=0.05\,m. AtF=20\,Nit no longer returns fully to length. Explain what changed physically and how the graph shows it. - In an experiment, your
F-vs-xline interceptsF=0.8\,Natx=0. Identify two plausible error sources and how to correct them. - Two springs in series (
k_1=300,k_2=200\,N·m^{-1}) support a mass. Derivek_{eq}and compute the extension underF=10\,N. - Design: Choose a target deflection of
15\,mmat a static load of120\,N. Specify a single-springkand justify a safety factor considering yield.
Complete one prompt:
- “I used evidence from my graph to conclude that …”
- “One source of error and how I would reduce it is …”
- “In design, increasing
kwould … because …”