Starter quiz
- Which two pieces of apparatus could be used to take the measurements needed to find the speed of a falling model parachute?
tape measure ✓
newton meter
digital balance
stopwatch ✓
- Which of these forces act on a skydiver as they fall downwards?
- drag ✓
- tension
- gravity ✓
- thrust
- magnetism
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- 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.
- When there is no resultant force. ✓
- When the force of gravity is larger than the drag force.
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- 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
- 1.4 s ✓
- 5.8 s
- 70 s
- 350 s
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- 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
- 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.
- '0.75 m/s' ✓
Exit quiz
- Match the key words to the explanations.
- gravitational force⇔A force that pulls objects towards Earth. ✓
- drag force⇔A force caused by friction due to air. ✓
- resultant force⇔The overall effect of a set of forces on an object. ✓
- parachute⇔A device used to increase drag during a fall. ✓
- velocity⇔The speed an object falls at. ✓
- 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.
- Gravitational force is constant, drag force increases. ✓
- Gravitational force is constant, drag force decreases.
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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?- They stop.
- They slow down.
- They speed up. ✓
- They stay at the same speed.
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The parachutes all have the same weight. Which will have the largest fall speed when dropped?- left (smallest) ✓
- center
- right (largest)
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- 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.
- The smaller parachute will hit the ground first. ✓
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- Why does a parachute reduce the terminal velocity of a falling skydiver?
- It makes them more streamlined.
- It increases the speed of the skydiver.
- It increases the drag force on the skydiver. ✓
- It reduces the gravitational force.
- It decreases the drag force on the skydiver.
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- The gravitational force on a falling object is constant.
- The drag force on a falling obejct depends on its speed and shape.
- Objects falling through the air will reach a terminal velocity when the drag and gravitational forces are equal.
- The terminal velocity can be changed by changing the drag force (e.g. with a parachute).
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.
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.
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