What are the different types of forces covered in Forces II in the IB MYP Science curriculum?

In the IB MYP Science curriculum, Forces II typically covers a variety of forces including gravitational force, frictional force, tension, normal force, and applied force. Each of these forces plays a crucial role in understanding how objects interact with each other and their environments.

How does friction affect motion according to the Forces II topic?

Friction is a force that opposes the motion of an object. In the context of Forces II, students learn that friction can slow down or stop the motion of objects. It acts in the opposite direction to the movement and is dependent on the surfaces in contact and the normal force pressing them together.

Can you explain the concept of tension as discussed in Forces II?

Tension is a force that is transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends. In Forces II, students explore how tension works in systems like pulleys and how it contributes to the equilibrium of forces in various scenarios.

What role does gravitational force play in the Forces II subtopic?

Gravitational force is a key concept in Forces II, where it is described as the attractive force between two masses. It is responsible for keeping planets in orbit and objects grounded on Earth. Students learn how to calculate gravitational force using the formula F = G(m1*m2)/r^2, where G is the gravitational constant.

How is the concept of normal force explained in the Forces II curriculum?

Normal force is the support force exerted upon an object that is in contact with another stable object. In Forces II, students learn that the normal force acts perpendicular to the surface of contact and is crucial in balancing other forces like gravity, especially when analyzing objects on inclined planes.

Why is "Giving a resultant force without direction." a common mistake in Forces II?

Why it happens: The arithmetic gives a number that 'feels' complete. How to avoid it: Resultant force is a VECTOR — always state direction (e.g. 15 N to the right).

Why is "Using F = ke beyond the elastic limit." a common mistake in Forces II?

Why it happens: The formula seems universal. How to avoid it: Hooke's law applies ONLY in the linear region. Beyond the limit the relationship is no longer proportional.

Why is "Saying friction is always unwanted." a common mistake in Forces II?

Why it happens: Textbooks emphasise the energy waste. How to avoid it: Friction lets shoes grip, brakes work and pencils write. It's both useful AND wasteful — depends on context.

ForcesIB MYP Sciences (Years 1-5)

Forces II

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next.

PreviousNext

Learn this Topic

Start with the slides for the quick version, then go deeper with the full study notes.

Short Study Notes in the form of Slides

Read the notes first. If the method in a worked example clicks, you're ready for the questions.

Short Study Notes — Forces II

Start with these resources to cover the key concepts, then work through the practice questions.

Page 1 / 0

Detailed Notes

Full prose, callouts and a recap — built for A* mastery, not just a quick scan.

Take these study notes with you

Download a branded PDF — full prose, callouts, recap and memorise list for Forces II, ready to print or save offline.

Forces II — IB MYP Sciences: resultant force, springs and a first look at F = ma

A step up from Forces I, this spiral note for IB MYP introduces resultant force on a straight line, how springs obey Hooke's law for small stretches, and a first taste of F = ma. Heavier maths is saved for the full Year 4-5 Forces topic.

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Find the resultant of two forces along the same line.
MYP Sciences A — Describe Hooke's law qualitatively (force ∝ extension up to a limit).
MYP Sciences A — State that a resultant force makes an object accelerate.
MYP Sciences B — Plan an investigation to test whether spring extension is proportional to force.
MYP Sciences D — Evaluate situations where friction is useful and where it is wasteful.

Resultant force on a line

Add forces going the same way; subtract those going opposite ways.

When two forces act along the same straight line, the resultant is easy to find. If both push right, ADD them. If one pushes right and the other left, SUBTRACT.

Example. A car has 800 N of engine thrust forwards and 300 N of friction/drag backwards. Resultant = 800 − 300 = 500 N forwards.

If the resultant force is zero, the object doesn't change its motion — it stays at rest, or carries on at a constant velocity.

If the resultant force is non-zero, the object speeds up (or slows down, or changes direction) in the direction of the resultant.

Same direction → add. Opposite directions → subtract.
Resultant = 0 → no change in motion.
Resultant ≠ 0 → acceleration in that direction.

Springs and Hooke's law

Stretch is proportional to force — until the spring goes past its limit.

Hang a 100 g mass on a spring and it stretches by some amount. Hang 200 g on the same spring and it stretches by exactly twice as much. Hang 300 g, and it stretches three times as much. This proportionality between FORCE and EXTENSION is Hooke's law:

$F = k \, e$

with F = applied force (N), e = extension from natural length (m), and k = spring constant (N/m). Stiffer springs have a larger k.

This proportional behaviour only works up to the elastic limit. Beyond that, the spring stretches more for each extra force and may not return to its original length when the force is removed.

A standard MYP lab investigation:

Independent variable: force (controlled by 100 g masses → 0.98 N per mass).
Dependent variable: spring extension (measured with a ruler).
Controlled: same spring, same room temperature, same supporting clamp.
Plot force on the y-axis, extension on the x-axis. Straight line through the origin = obeys Hooke's law.

Straight-line region: F = ke. Past the elastic limit, extension increases more for each extra force.

Hooke's law: F = ke (only up to the elastic limit).
Bigger spring constant k = stiffer spring.
Beyond elastic limit, spring doesn't return to original length.

First taste of F = ma

The bigger the force on the same mass, the bigger the acceleration.

Push the same trolley with different forces and you'll feel the difference: more force → more acceleration. Push different-mass trolleys with the same force, and the heavier one accelerates less.

These observations are summed up by:

$F = m \, a$

where F is the resultant force (N), m is the mass (kg) and a is the acceleration (m/s²).

You'll do detailed calculations with F = ma in the Year 4-5 Forces topic. For now the key idea is:

Same mass, more force → more acceleration.
Same force, more mass → less acceleration.
No resultant force → no acceleration (Newton's first law).

F = m × a (resultant force, in newtons).
Same mass: more F → more a.
Same F: more m → less a.

Friction — friend and foe

Friction opposes motion. Sometimes useful; sometimes wasteful.

Useful friction:

Shoes grip the floor.
Brakes slow the wheels of a car or bike.
Tyres grip the road; without it, the car would just spin its wheels.
Pencil leaves a mark because friction breaks off small graphite particles.

Wasteful friction:

Heats up machine parts; energy is dissipated.
Causes wear on moving parts (e.g. brake pads, axles).
Slows down moving objects, requiring more energy to maintain motion.

Engineers reduce unwanted friction with lubricants (oil, grease), polished surfaces, ball bearings or streamlined shapes (cars, swimmers).

Friction opposes motion between two contacting surfaces.
Useful: grip, braking, writing.
Wasteful: heating, wear, slowdown.
Reduce with lubricants, bearings, streamlining.

How it’s examined

MYP Year 3-4 internal assessments often include a Hooke's-law lab report (criteria B, C). The Year-5 eAssessment tests resultant-force reasoning under criterion A.

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Forces II, ready to print or save as PDF.

Step-by-step worked examples — Forces II

Step-by-step solutions to past-paper-style questions on forces ii, written exactly the way a tutor would explain them at the board.

1Finding a resultant force
Getting started• resultant
Question
A box is pushed to the right with 25 N. Friction pushes back with 10 N. Calculate the resultant force.
Step-by-step solution
1. Step 1
  Forces are opposite directions, so subtract.
2. Step 2
  Resultant = 25 − 10 = 15 N to the right.
Answer
15 N to the right.
2Spring extension
Building confidence• Hooke's law
Question
A spring with spring constant 50 N/m has a 2.0 N force applied. Find the extension.
Step-by-step solution
1. Step 1
  Use F = ke → e = F/k.
  $e = 2.0 / 50$
2. Step 2
  e = 0.04 m = 4 cm.
Answer
0.04 m (4 cm).
3Using F = ma
Building confidence• F = ma
Question
A 4.0 kg trolley has a resultant force of 12 N. Find its acceleration.
Step-by-step solution
1. Step 1
  Rearrange F = ma → a = F/m.
  $a = 12 / 4.0$
2. Step 2
  a = 3.0 m/s².
Answer
3.0 m/s².

Key Formulae — Forces II

The formulae you need to memorise for forces ii on the IB MYP Sciences paper, with every variable defined in plain English and a note on when to use it.

Hooke's law
$F = k × e$
$F$
force on spring (N)
$k$
spring constant (N/m)
$e$
extension (m)
When to use
Springs within their elastic limit.
Newton's 2nd law
$F = m × a$
$F$
resultant force (N)
$m$
mass (kg)
$a$
acceleration (m/s²)
When to use
Linking force, mass and acceleration.

Key Definitions and Keywords — Forces II

Definitions to memorise and the exact keywords mark schemes credit for forces ii answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

Resultant force
Examiner keyword
The single force that would have the same effect as all forces on an object combined.
Hooke's law
Examiner keyword
Spring extension is directly proportional to the applied force, up to the elastic limit. F = ke.
Spring constant (k)
A measure of stiffness — larger k = stiffer spring. Unit N/m.
Elastic limit
The maximum force beyond which a spring no longer returns to its original length.
Friction
A force that opposes the motion of two surfaces in contact. Can be useful or wasteful.

Common Mistakes and Misconceptions — Forces II

The traps other students keep falling into on forces ii questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Giving a resultant force without direction.
Why it happens
The arithmetic gives a number that 'feels' complete.
How to avoid it
Resultant force is a VECTOR — always state direction (e.g. 15 N to the right).
✕Using F = ke beyond the elastic limit.
Why it happens
The formula seems universal.
How to avoid it
Hooke's law applies ONLY in the linear region. Beyond the limit the relationship is no longer proportional.
✕Saying friction is always unwanted.
Why it happens
Textbooks emphasise the energy waste.
How to avoid it
Friction lets shoes grip, brakes work and pencils write. It's both useful AND wasteful — depends on context.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Forces II — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

ForcesIB MYP Sciences (Years 1-5)

Forces II

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next.

PreviousNext

Learn this Topic

Start with the slides for the quick version, then go deeper with the full study notes.

Short Study Notes in the form of Slides

Read the notes first. If the method in a worked example clicks, you're ready for the questions.

Short Study Notes — Forces II

Start with these resources to cover the key concepts, then work through the practice questions.

Page 1 / 0

Detailed Notes

Full prose, callouts and a recap — built for A* mastery, not just a quick scan.

Take these study notes with you

Download a branded PDF — full prose, callouts, recap and memorise list for Forces II, ready to print or save offline.

Forces II — IB MYP Sciences: resultant force, springs and a first look at F = ma

What you’ll learn

Mapped to the IB MYP Sciences subject guide (2026 onwards).

MYP Sciences A — Find the resultant of two forces along the same line.
MYP Sciences A — Describe Hooke's law qualitatively (force ∝ extension up to a limit).
MYP Sciences A — State that a resultant force makes an object accelerate.
MYP Sciences B — Plan an investigation to test whether spring extension is proportional to force.
MYP Sciences D — Evaluate situations where friction is useful and where it is wasteful.

Resultant force on a line

Add forces going the same way; subtract those going opposite ways.

When two forces act along the same straight line, the resultant is easy to find. If both push right, ADD them. If one pushes right and the other left, SUBTRACT.

Example. A car has 800 N of engine thrust forwards and 300 N of friction/drag backwards. Resultant = 800 − 300 = 500 N forwards.

If the resultant force is zero, the object doesn't change its motion — it stays at rest, or carries on at a constant velocity.

If the resultant force is non-zero, the object speeds up (or slows down, or changes direction) in the direction of the resultant.

Same direction → add. Opposite directions → subtract.
Resultant = 0 → no change in motion.
Resultant ≠ 0 → acceleration in that direction.

Springs and Hooke's law

Stretch is proportional to force — until the spring goes past its limit.

$F = k \, e$

with F = applied force (N), e = extension from natural length (m), and k = spring constant (N/m). Stiffer springs have a larger k.

This proportional behaviour only works up to the elastic limit. Beyond that, the spring stretches more for each extra force and may not return to its original length when the force is removed.

A standard MYP lab investigation:

Independent variable: force (controlled by 100 g masses → 0.98 N per mass).
Dependent variable: spring extension (measured with a ruler).
Controlled: same spring, same room temperature, same supporting clamp.
Plot force on the y-axis, extension on the x-axis. Straight line through the origin = obeys Hooke's law.

Straight-line region: F = ke. Past the elastic limit, extension increases more for each extra force.

Hooke's law: F = ke (only up to the elastic limit).
Bigger spring constant k = stiffer spring.
Beyond elastic limit, spring doesn't return to original length.

First taste of F = ma

The bigger the force on the same mass, the bigger the acceleration.

Push the same trolley with different forces and you'll feel the difference: more force → more acceleration. Push different-mass trolleys with the same force, and the heavier one accelerates less.

These observations are summed up by:

$F = m \, a$

where F is the resultant force (N), m is the mass (kg) and a is the acceleration (m/s²).

You'll do detailed calculations with F = ma in the Year 4-5 Forces topic. For now the key idea is:

Same mass, more force → more acceleration.
Same force, more mass → less acceleration.
No resultant force → no acceleration (Newton's first law).

F = m × a (resultant force, in newtons).
Same mass: more F → more a.
Same F: more m → less a.

Friction — friend and foe

Friction opposes motion. Sometimes useful; sometimes wasteful.

Useful friction:

Shoes grip the floor.
Brakes slow the wheels of a car or bike.
Tyres grip the road; without it, the car would just spin its wheels.
Pencil leaves a mark because friction breaks off small graphite particles.

Wasteful friction:

Heats up machine parts; energy is dissipated.
Causes wear on moving parts (e.g. brake pads, axles).
Slows down moving objects, requiring more energy to maintain motion.

Engineers reduce unwanted friction with lubricants (oil, grease), polished surfaces, ball bearings or streamlined shapes (cars, swimmers).

Friction opposes motion between two contacting surfaces.
Useful: grip, braking, writing.
Wasteful: heating, wear, slowdown.
Reduce with lubricants, bearings, streamlining.

How it’s examined

MYP Year 3-4 internal assessments often include a Hooke's-law lab report (criteria B, C). The Year-5 eAssessment tests resultant-force reasoning under criterion A.

Sources: IB MYP Sciences guide (IBO, official subject guide). Last reviewed 2026-05-25.

Master this Topic

Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.

Take this whole topic with you

Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Forces II, ready to print or save as PDF.

Step-by-step worked examples — Forces II

Step-by-step solutions to past-paper-style questions on forces ii, written exactly the way a tutor would explain them at the board.

1Finding a resultant force
Getting started• resultant
Question
A box is pushed to the right with 25 N. Friction pushes back with 10 N. Calculate the resultant force.
Step-by-step solution
1. Step 1
  Forces are opposite directions, so subtract.
2. Step 2
  Resultant = 25 − 10 = 15 N to the right.
Answer
15 N to the right.
2Spring extension
Building confidence• Hooke's law
Question
A spring with spring constant 50 N/m has a 2.0 N force applied. Find the extension.
Step-by-step solution
1. Step 1
  Use F = ke → e = F/k.
  $e = 2.0 / 50$
2. Step 2
  e = 0.04 m = 4 cm.
Answer
0.04 m (4 cm).
3Using F = ma
Building confidence• F = ma
Question
A 4.0 kg trolley has a resultant force of 12 N. Find its acceleration.
Step-by-step solution
1. Step 1
  Rearrange F = ma → a = F/m.
  $a = 12 / 4.0$
2. Step 2
  a = 3.0 m/s².
Answer
3.0 m/s².

Key Formulae — Forces II

The formulae you need to memorise for forces ii on the IB MYP Sciences paper, with every variable defined in plain English and a note on when to use it.

Hooke's law
$F = k × e$
$F$
force on spring (N)
$k$
spring constant (N/m)
$e$
extension (m)
When to use
Springs within their elastic limit.
Newton's 2nd law
$F = m × a$
$F$
resultant force (N)
$m$
mass (kg)
$a$
acceleration (m/s²)
When to use
Linking force, mass and acceleration.

Key Definitions and Keywords — Forces II

Definitions to memorise and the exact keywords mark schemes credit for forces ii answers — sharpened from recent examiner reports for the 2026 IB MYP Sciences sitting.

Resultant force
Examiner keyword
The single force that would have the same effect as all forces on an object combined.
Hooke's law
Examiner keyword
Spring extension is directly proportional to the applied force, up to the elastic limit. F = ke.
Spring constant (k)
A measure of stiffness — larger k = stiffer spring. Unit N/m.
Elastic limit
The maximum force beyond which a spring no longer returns to its original length.
Friction
A force that opposes the motion of two surfaces in contact. Can be useful or wasteful.

Common Mistakes and Misconceptions — Forces II

The traps other students keep falling into on forces ii questions — taken from recent IB MYP Sciences examiner reports and mark schemes — and how to avoid them.

✕Giving a resultant force without direction.
Why it happens
The arithmetic gives a number that 'feels' complete.
How to avoid it
Resultant force is a VECTOR — always state direction (e.g. 15 N to the right).
✕Using F = ke beyond the elastic limit.
Why it happens
The formula seems universal.
How to avoid it
Hooke's law applies ONLY in the linear region. Beyond the limit the relationship is no longer proportional.
✕Saying friction is always unwanted.
Why it happens
Textbooks emphasise the energy waste.
How to avoid it
Friction lets shoes grip, brakes work and pencils write. It's both useful AND wasteful — depends on context.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Forces II — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Forces II

Short Study Notes in the form of Slides

Short Study Notes — Forces II

Detailed Notes

What you’ll learn

How it’s examined

1Finding a resultant force

2Spring extension

3Using F = ma

Hooke's law

Newton's 2nd law

Resultant force

Hooke's law

Spring constant (k)

Elastic limit

Friction

✕Giving a resultant force without direction.

✕Using F = ke beyond the elastic limit.

✕Saying friction is always unwanted.

Practice questions

Past paper style quiz

Assess your understanding

Forces II — frequently asked questions

Forces II

Short Study Notes in the form of Slides

Short Study Notes — Forces II

Detailed Notes

What you’ll learn

How it’s examined

1Finding a resultant force

2Spring extension

3Using F = ma

Hooke's law

Newton's 2nd law

Resultant force

Hooke's law

Spring constant (k)

Elastic limit

Friction

✕Giving a resultant force without direction.

✕Using F = ke beyond the elastic limit.

✕Saying friction is always unwanted.

Practice questions

Past paper style quiz

Assess your understanding

Forces II — frequently asked questions