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Year 8

Changing the speed of a parachute

I can clearly describe how drag forces affect the motion of falling objects.

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New
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Year 8

Changing the speed of a parachute

I can clearly describe how drag forces affect the motion of falling objects.

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Share activities with pupils
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Lesson details

Key learning points

  1. The gravitational force on a falling object is constant.
  2. The drag force on a falling obejct depends on its speed and shape.
  3. Objects falling through the air will reach a terminal velocity when the drag and gravitational forces are equal.
  4. The terminal velocity can be changed by changing the drag force (e.g. with a parachute).

Keywords

  • Gravitational force - The gravitational force on something pulls it downwards, towards Earth.

  • Drag force - When an object moves through a fluid there is a drag force that opposes the movement.

  • Resultant force - A resultant force is the overall effect of a set of forces on an object, taking their directions into account.

  • Parachute - A parachute is used to increase the size of drag forces. This slows down the object it is attached to.

  • Terminal velocity - An object reaches a terminal velocity when the drag and gravitational forces are equal.

Common misconception

Video of skydiving may lead pupils to think opening a parachute makes a skydiver 'shoot upwards'.

Explain that this 'upwards motion' is relative motion to a cameraman. Discuss what a sudden upwards motion would do to a falling skydiver.

Showing and pausing video clips of skydiving from action films enhances this lesson substantially. Discuss how the divers manipulate their speeds by adjusting their fall angle.
Teacher tip

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

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).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which two pieces of apparatus could be used to take the measurements needed to find the speed of a falling model parachute?
Correct answer: tape measure
newton meter
digital balance
Correct answer: stopwatch
Q2.
Which of these forces act on a skydiver as they fall downwards?
Correct answer: drag
tension
Correct answer: gravity
thrust
magnetism
Q3.
When does a falling object reach a steady speed?
When there is no drag.
When there is no gravity force.
When the drag force is larger than the force of gravity.
Correct answer: When there is no resultant force.
When the force of gravity is larger than the drag force.
Q4.
A student measures how long a parachute takes to fall a distance of 2.0 m five separate times. Their readings are 1.5 s , 1.2 s, 1.4 s, 1.3 s and 1.4 s. Calculate the average fall time.
1.2 s
Correct answer: 1.4 s
5.8 s
70 s
350 s
Q5.
A set of model parachutes with different surface areas were dropped through a distance of 1.5 m. Starting with the fastest, sort the parachutes in order of average fall speed.
1 - 0.70 s
2 - 0.72 s
3 - 0.95 s
4 - 0.99 s
5 - 1.44 s
6 - 1.48 s
Q6.
A model parachute falls through a distance of 1.8 m in a time of 2.4 s. Calculate the average speed of the parachute during the fall. Give the correct unit.
Correct Answer: 0.75 m/s, 0.75 metres per second, 0.75 mps, 0.75
Q1 image 2 UYSEG Q1 image 4 UYSEG

Exit quiz

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6 Questions

Q1.
Match the key words to the explanations.
Correct Answer:gravitational force,A force that pulls objects towards Earth.

A force that pulls objects towards Earth.

Correct Answer:drag force,A force caused by friction due to air.

A force caused by friction due to air.

Correct Answer:resultant force,The overall effect of a set of forces on an object.

The overall effect of a set of forces on an object.

Correct Answer:parachute,A device used to increase drag during a fall.

A device used to increase drag during a fall.

Correct Answer:velocity,The speed an object falls at.

The speed an object falls at.

Q2.
Which of these describes what happens to the forces on a skydiver as they are speeding up?
Gravitational force is constant, drag force is constant.
Gravitational force decreases, drag force is constant.
Gravitational force increases, drag force is constant.
Correct answer: Gravitational force is constant, drag force increases.
Gravitational force is constant, drag force decreases.
Q3.
A skydiver has a gravitational force of 700 N acting on them and a drag force of 600 N. What happens to the motion of the skydiver?
An image in a quiz
They stop.
They slow down.
Correct answer: They speed up.
They stay at the same speed.
Q4.
The parachutes all have the same weight. Which will have the largest fall speed when dropped?
An image in a quiz
Correct answer: left (smallest)
center
right (largest)
Q5.
Two people with the same mass, in parachutes of different surface areas, drop at the same time from a plane and reach terminal velocity. Which will hit the ground first?
Both parachutes will reach the ground at the same time.
The bigger parachute will hit the ground first.
Correct answer: The smaller parachute will hit the ground first.
Q6.
Why does a parachute reduce the terminal velocity of a falling skydiver?
It makes them more streamlined.
It increases the speed of the skydiver.
Correct answer: It increases the drag force on the skydiver.
It reduces the gravitational force.
It decreases the drag force on the skydiver.