New
New
Year 10
Edexcel
Higher

# Stretching a spring analysis and calculations (F=kx)

I can describe and calculate the properties of a spring using Hooke’s law.

New
New
Year 10
Edexcel
Higher

# Stretching a spring analysis and calculations (F=kx)

I can describe and calculate the properties of a spring using Hooke’s law.

## Lesson details

### Key learning points

1. A spring is elastically deformed if it returns to its original shape after the applied force is removed
2. A spring is inelastically deformed if it does not return to its original shape after the applied force is removed
3. Elastic deformation is proportional to the force applied to stretch or compress a spring
4. The spring constant (k) is the force needed to extend or compress an elastic object by one metre
5. Force on a spring = spring constant × extension

### Common misconception

Pupils often think the bigger the spring constant, the more a spring stretches for a given force.

Provide opportunities for pupils to apply understanding that the spring constant describes the stiffness of a spring. The bigger the spring constant, the harder it is to stretch (or compress) the spring.

### Keywords

• Directly proportional - A variable is directly proportional to another if it doubles or triples when the other one does the same.

• Elastic deformation - The stretch of a spring that returns to its original shape when the stretching force is removed.

• Inelastic deformation - The stretch of a spring as it is permanently stretched out of shape.

• Spring constant - A measure of how stiff a spring is and how hard it is to stretch or compress.

• Hooke’s Law - For elastic deformations, extension (or compression) is directly proportional to the force applied.

Exam questions for Hooke’s Law may refer to the stretching, compressing or bending of elastic objects and it is important to give pupils opportunities to explore each type of deformation.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
Which of the following is the unit of force?
grams
joules
kilograms
Q2.
An object is stretched by a force, but returns to its original shape when the force is removed. This type of deformation is called deformation.
Q3.
An object is stretched by a force and will not return to its original shape when the force is removed. This type of deformation is called deformation.
Q4.
Which of the following describes the extension of a spring?
The length of the stretched spring.
The length of the unstretched spring.
Correct answer: The difference between the stretched and unstretched lengths.
Q5.
Which of the following describes a variable in an experiment?
Correct answer: A quantity that can change.
A quantity that must be changed.
A quantity that is constant.
A quantity that must be kept the same.
Q6.
Rearrange the formula a = b ÷ c to make b the subject.
Correct answer: b = a × c
b = a ÷ c
b = c ÷ a

## Exit quiz

### 6 Questions

Q1.
Two variables are directly proportional. Which of the following statements about the two variables are correct?
Correct answer: When one variable doubles, the other variable doubles.
When one variable increases by 10, the other variable increases by 10.
Correct answer: When one variable becomes 5 times greater, the other becomes 5 times greater.
Correct answer: When one variable halves, the other variable halves.
Q2.
The following graphs show extension against applied force for three different springs. The scales are the same on all of the graphs. Which graph represents the spring with the lowest spring constant?
Correct Answer: An image in a quiz
Q3.
For elastic deformation, extension (or compression) is directly proportional to the force applied. What is the name of this law, and how is it expressed as an equation?
Newton’s law
\$\$F = x ÷ k\$\$
Correct answer: \$\$F = k × x\$\$
\$\$F = k ÷ x\$\$
Q4.
Cars have stiff suspension springs to ensure a smoother ride. If the spring constant of one of these springs is 60 000 N/m, the force needed to compress the spring by 2.0 cm is N.
Correct Answer: 1200, 1,200, 1 200, 1200 N, 1200N
Q5.
A spring has an unstretched length of 0.6 m. When a force of 200 N is applied, it stretches to a length of 1.0 m. What is the spring constant of the spring?
0.002 N/m
0.005 N/m
200 N/m