Estimated time:

15 minutes setup, 30-45 minutes data collection, 30 minutes results analysis and discussion.

The Ejection Seat

Boing! Boing! Boing! The Ejection Seat is a fun carnival ride that uses the spring force to oscillate the rider up and down.

The Ejection Seat

Contents

In this activity, you will construct an Ejection Seat and to study the motion of a spring, and investigate how the mass of an object attached to the spring affects this motion. You will measure properties of motion using the accelerometer on the Arduino Science Carrier Board. By changing the mass of the object attached, the ride can oscillate in different ways!

Teacher's guide

UK NATIONAL CURRICULUM

Science - Physics - UK National Curriculum 2013 - Key stage 3

Forces being needed to cause objects to stop or start moving, or to change their speed or direction of motion (qualitative only).

NGSS Standards

Third Grade - Next Generation Science Standards - 3.Forces and Interactions

3-PS2-1.

Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

3-PS2-2.

Make observations and/or measurements of an object’s motion to provide evidence that a pattern can be used to predict future motion.

Middle School Physical Science - Next Generation Science Standards - MS.Forces and Interactions

MS-PS2-2.

Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.

Getting started/ pre- class prep

Select a suitable location to release the spring that avoids any collision of the spring with the floor. Ensure the board is fixed securely to the spring.

Material list

1Arduino MKR WiFi 1010

1Arduino Science Carrier Board

1Metal Slinky Spring

1 Flat micro USB cable

2 Silicone Standoffs

Material not included

1Mobile device with Arduino Science Journal installed

1Portable Power Bank

1Li-Po Battery

1Kitchen Scale

Optional material

1Hook-and-Loop Velcro™️ Dot

Topics and keywords

  • Acceleration

    : The rate change of velocity with respect to time.

  • Accelerometer

    : A device that measures acceleration due to a force.

  • Amplitude

    : The maximum displacement of an object from its equilibrium position.

  • Equilibrium position

    : The position which an object will remain if undisturbed.

  • Force

    : An interaction that causes an object to be pushed or pulled in a certain direction with the effect of changing the motion of the object.

  • Friction

    : A force that resists the motion of two surfaces that are in contact with each other.

  • Frequency

    : The number of cycles or oscillations in a specific amount of time: frequency = 1 / period.

  • Gravitational Force

    : The force of gravity or weight acting on an object.

  • Inertial Measurement Unit (IMU)

    : An electronic sensor that measures the acceleration and rotation of an object using a combination of accelerometers, gyroscopes and sometimes magnetometers.

  • Momentum

    : The product of mass and velocity (mass ✕ velocity) for an object.

  • Oscillation

    : A repetitive cycle or change between two or more different states or positions.

  • Pendulum

    : An object hung from a fixed point that swings back and forth due to the force of gravity, until friction slows it down and eventually causing it to stop swinging.

  • Period

    : The time required to complete 1 whole cycle or oscillation.

  • Spring

    : An elastic object that exerts an opposing force proportional to its change in position.

  • Velocity

    : The rate of change of position over time.

Learning outcomes

On completion of the experiment students will be able to:

  • Describe the motion of a spring.
  • Measure the period of an oscillating spring.
  • Calculate the frequency of an oscillating spring.
  • Monitor the acceleration of a spring throughout its motion.
  • Identify the forces acting on an oscillating spring.
  • Explore the effect of spring mass on its period of oscillation.
  • Investigate the influence of air resistance and spring type on the motion of a spring.

Did you know that?

Power Shot Reverse Bungee, top of travel. By Andrew Dunn, Cambridge Midsummer Fair 2005. CC BY-SA 2.0
Power Shot Reverse Bungee, top of travel. By Andrew Dunn, Cambridge Midsummer Fair 2005. CC BY-SA 2.0
The Ejection Seat ride or reverse bungee was invented in 1978. The ride has 2 towers on the sides mounted on a steady platform, with two elastic ropes attached to a tubular steel passenger car. The spherical cage of the car is secured to the platform with an electromagnetic latch whilst the elastic ropes are stretched. Passengers must be securely fastened to the car at all times. The passenger car is launched vertically, when the latch is released. The riders can be catapulted to an altitude of up to 150 meters, and the car is free to bounce in all directions. After several bounces the elastic ropes are loosened and passengers are brought back to the launch platform.

The factors which make this ride so thrilling are: force, mass and acceleration. The mass is made by the passenger’s car plus its passengers inside. The stretched bungee when released exerts a large force on the ejection seat. This force produces an acceleration that launches the seat upwards against the force of gravity. The acceleration causes the speed of the seat to increase dramatically. The faster you go, the more you’ll be pushed back to your seat!

Background

Springs have been used by humans since before the beginning of recorded history. Early humans used springs for hunting (bow-and-arrow) and for many other tools, from tweezers to rifles to chariots. Coiled springs, like the kind you will be using in this activity, were invented in the 1500s, and were quickly incorporated into many gadgets, such as locks, clocks and car suspensions.

DO NOT TRY THIS AT HOME OR AT SCHOOL!!!! A diver prepares to jump. Except for the vines, land diving is performed without safety equipment. The Tower, Pentecost Island Vanuatu. By Paul Stein, 1992. CC BY-SA 2.0
DO NOT TRY THIS AT HOME OR AT SCHOOL!!!! A diver prepares to jump. Except for the vines, land diving is performed without safety equipment. The Tower, Pentecost Island Vanuatu. By Paul Stein, 1992. CC BY-SA 2.0

Springs were also used in a ritual called “vine jumping” by ancient Aztecs and native peoples of the South Pacific. Since 1979, people have used springy cords for thrilling drops from structures such as the Golden Gate Bridge, the Eiffel Tower, and countless carnival rides since!

'Robert Hooke, Engineer'. A memorial portrait presented to the Department of Engineering Science at Oxford University in 2009. By Rita Greer, 2009. FAL 1.3
'Robert Hooke, Engineer'. A memorial portrait presented to the Department of Engineering Science at Oxford University in 2009. By Rita Greer, 2009. FAL 1.3

In 1676, a scientist named Robert Hooke developed a mathematical model of springs and their motion, which is still in use today! Spring motion is a special type of oscillation motion caused by the spring force, and is studied in a branch of physics called Classical Mechanics.

In this activity, we will be exploring the effect of this spring force by measuring the acceleration of an object fixed to an oscillating spring. We will examine the patterns that we see in the oscillation data, such as the period, frequency and amplitude, to find out how springs behave when attached to objects with different mass. We will also consider other forces acting on a spring in motion.

Sensor Setup

The sensor we are using for this experiment is already attached to the surface of the board (IMU), and no extra sensors will need to be set up.

IMU Sensor
IMU Sensor

Physical Setup

Weigh the Arduino Science Carrier Board with and without the standoffs using the mass scale.
Select and attach a spring to the Arduino Science Carrier Board.
Place your spring at the edge of a table or desk. Hold it with your hand.
Adjust the length of your spring. Let it bounce.
Repeat the same steps increasing the mass.
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Weigh the Arduino Science Carrier Board with and without the standoffs using the mass scale.
Select and attach a spring to the Arduino Science Carrier Board.
Place your spring at the edge of a table or desk. Hold it with your hand.
Adjust the length of your spring. Let it bounce.
Repeat the same steps increasing the mass.

Collecting Data

  1. Open the Arduino Science Journal app.
  2. Start a new experiment.
  3. Select the sensor icon in the bottom tool drawer, and select the Arduino board's built-in X accelerometer or linear acceleration.
  4. With the standoffs removed, pull the carrier board down with the spring slightly extended (approx. 2 cm up from the equilibrium position).
  5. Tap the record button.
  6. Let go of the Arduino Science Carrier Board! Allow the spring to oscillate up and down for 30 seconds.
  7. Tap the stop recording button.
  8. Change the title of the recording to “Low Mass”.
  9. Your graph should show oscillations as your spring oscillates up and down. Find two peaks that are next to each other, and drag the cursor along the graph to measure the time between the two peaks. This time difference between the two neighboring peaks is equal to the period of oscillation.
  10. Measure and record the time it takes for the spring to come to a complete stop.
  11. Add standoffs to the board and repeat steps 3 - 10. Change the title of the new recording to “High Mass”.

Results and Analysis

  • Describe how you measured the period of oscillation of the spring.
  • Can you think of another technique to measure period?
  • What is the period of oscillation for each experiment?
  • Does the mass of the board affect the period of oscillation? Why?
  • Identify 3 forces that act on the spring as it oscillates.
  • Use the data graph, that shows spring acceleration over time, to find the position of the spring when its acceleration is highest, zero and lowest.
  • Since acceleration is directly related to force, find the position of the spring when the force acting on the spring is highest, zero and lowest.
  • What are some common uses of springs?

Student worksheet

Download the Student Worksheet

Future directions, next steps

  • Use an assortment of springs made of different materials and spring constants, to explore the influence of spring type on spring period.
  • Vary the initial position (extension) of the spring before release, and measure the period of oscillation of the spring. How does the initial extension affect the period?
  • Add a cardboard sail to the spring to introduce air resistance. Investigate the influence of the sail on the period of the spring and the time it takes for the Ejection Seat to come to a complete stop.