Terminal velocity

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Terminal velocity (KS3 Science, Physics) — use them in your lesson, or run the topic as an interactive class activity your students play as a live game.

Lesson notes

Key Concepts

**Newton's first law**: An object's speed stays constant unless a **resultant force** acts on it.
**Newton's second law**: Acceleration is proportional to the resultant force; larger force → larger acceleration.
**Newton's third law**: Forces between two objects are equal in size and opposite in direction.
**Terminal velocity** is the maximum constant speed reached when forces are balanced.

Stages of a Skydive

1. **Just jumped**: Only **weight** acts → skydiver **accelerates** downwards.
2. **Speeding up**: **Air resistance** increases with speed; resultant force decreases → acceleration decreases.
3. **Terminal velocity**: Air resistance = weight → **balanced forces**, no resultant force → constant speed (terminal velocity).
4. **Parachute opens**: Larger surface area → air resistance increases greatly → resultant force **upwards** → **deceleration**.
5. **Second terminal velocity**: Slower speed reduces air resistance until it equals weight again → new, slower constant speed.

Graph of a Skydive

A **speed–time graph** shows speed increasing then levelling off at terminal velocity.
After parachute opens, speed drops rapidly then becomes constant at a lower terminal velocity.
The gradient of the graph represents acceleration (positive gradient = accelerating, negative = decelerating, flat = constant speed).

Factors Affecting Terminal Velocity

**Weight**: Heavier objects have a higher terminal velocity (larger weight requires larger air resistance to balance).
**Surface area**: Larger surface area increases air resistance, reducing terminal velocity (e.g., parachute).
**Shape**: Streamlined shapes reduce air resistance, allowing higher terminal velocity.

Examples and Applications

A car travelling at constant speed on a motorway has **balanced forces** (driving force = resistive forces).
If a resultant forward force acts on a car, it **accelerates** (speeds up).
Sky divers reach terminal velocity twice: first without parachute (fast), then with parachute (slow).

Particle arrangement in solids, liquids, and gases. In a solid, particles are closely packed in a regular pattern; in a liquid, they are close but irregular; in a gas, they are far apart and random. This model helps explain density and state changes.

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.What happens to air resistance as the speed of an object increases?
Easy
- AIt increases
- BIt decreases
- CIt stays the same
- DIt becomes zero
2.A car is travelling at a constant speed. All the forces on the car are balanced. What happens to the speed of the car?
Easy
- AIt stays the same
- BIt increases
- CIt decreases
- DIt becomes zero
3.A car has a resultant force forwards. What happens to the speed of the car?
Easy
- AIt increases
- BIt decreases
- CIt stays the same
- DIt becomes zero
4.A skydiver has just jumped out of an aeroplane. The only force acting is their weight. What is the motion of the skydiver?
Medium
- AAccelerating downwards
- BConstant speed downwards
- CDecelerating downwards
- DStationary
5.A skydiver has reached terminal velocity. Which statement about the forces is correct?
Medium
- AWeight equals air resistance
- BWeight is greater than air resistance
- CWeight is less than air resistance
- DThere is no weight
6.A skydiver opens their parachute. What happens to the air resistance immediately after opening?
Hard
- AIt increases dramatically
- BIt decreases dramatically
- CIt stays the same
- DIt becomes zero
7.After opening the parachute, the skydiver decelerates. What is the direction of the resultant force?
Medium
- AUpwards
- BDownwards
- CHorizontal
- DZero
8.A skydiver reaches a second terminal velocity after opening the parachute. How does this second terminal velocity compare to the first?
Medium
- AIt is slower
- BIt is faster
- CIt is the same
- DIt is zero

Revision notes

## Terminal Velocity (Skydiving) - **Newton's First Law**: Speed stays constant unless a resultant force acts. - **Newton's Second Law**: Acceleration ∝ resultant force. - **Newton's Third Law**: Forces between objects are equal and opposite. ### Stages of a Skydive: 1. **Just jumped**: Only weight acts → accelerates downwards. 2. **Speeding up**: Air resistance increases, resultant force decreases → acceleration decreases. 3. **Terminal velocity**: Air resistance = weight → no resultant force → constant speed (terminal velocity). 4. **Parachute opens**: Surface area increases → air resistance > weight → resultant force upward → deceleration. 5. **New terminal velocity**: Slower speed reduces air resistance until balanced → second, slower terminal velocity. ### Key Points: - Air resistance increases with speed. - Terminal velocity is the maximum constant speed when forces balance. - Opening parachute increases air resistance, causing deceleration to a lower terminal velocity.

Terminal velocity: The constant maximum speed reached when the resultant force on an object is zero, e.g., when air resistance equals weight.
Newton's first law: The speed of an object will remain the same unless a resultant force acts on the object.
Newton's second law: The acceleration of an object is proportional to the resultant force on the object.
Newton's third law: If object A exerts a force on object B, then object B exerts a force of equal size and opposite direction on object A.
Air resistance: A frictional force that opposes motion through air; increases with speed and surface area.

Flashcards

What is terminal velocity?

Terminal velocity is the constant maximum speed reached when the force of air resistance equals the weight of the falling object, resulting in zero net force and zero acceleration.

According to Newton's first law, what happens to the speed of an object if no resultant force acts on it?

The speed of the object remains the same (constant speed).

According to Newton's second law, how is acceleration related to resultant force?

Acceleration is proportional to the resultant force; larger resultant force gives larger acceleration.

State Newton's third law.

If object A exerts a force on object B, then object B exerts a force of equal size and opposite direction on object A.

What is the only force acting on a skydiver just after jumping out of a plane (before falling fast)?

Their weight (downward force).

How does air resistance change as a skydiver's speed increases?

Air resistance increases as speed increases.

What happens to the resultant downward force on a skydiver as they speed up?

The resultant downward force decreases because air resistance increases, opposing weight.

What happens to the acceleration of a skydiver as they approach terminal velocity?

Acceleration decreases, eventually becoming zero at terminal velocity.

At terminal velocity, how do the forces on a skydiver compare?

The forces are balanced: air resistance equals weight, so resultant force is zero.

What does Newton's first law say about a skydiver at terminal velocity?

Since the resultant force is zero, the skydiver continues moving at constant speed (terminal velocity).

What happens to air resistance when a skydiver opens their parachute?

Air resistance increases dramatically because the parachute increases surface area.

What is the direction of the resultant force just after a parachute opens?

Upward, because air resistance becomes greater than weight.

What happens to the skydiver's motion just after the parachute opens?

The skydiver decelerates (slows down) due to the upward resultant force.

After decelerating with the parachute open, what happens to air resistance?

As the skydiver slows, air resistance decreases until it equals weight again.

Does a skydiver reach a second terminal velocity after opening the parachute?

Yes, a slower terminal velocity when forces are balanced again.

In the speed-time graph of a skydiver, what does a horizontal line indicate?

Constant speed, which occurs at terminal velocity (before and after parachute opening).

In the speed-time graph, what does a decreasing slope (downward curve) indicate?

Deceleration, which happens after the parachute opens.

In the speed-time graph, what does an increasing slope (upward curve) indicate?

Acceleration, which occurs at the start of the fall.

What is the relationship between resultant force and acceleration according to Newton's second law?

The acceleration of an object is proportional to the resultant force on it.

If a car is travelling at constant speed on a motorway, what can be said about the forces?

All forces on the car are balanced; resultant force is zero.

If a car has a resultant force forwards, what happens to its speed?

The car accelerates (speed increases).

Unlock all 40 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon