Conker rolling

Physics fun using free resources, what’s not to love! This outdoor activity can be taken inside if conditions outside are not conducive to learning.

Learning Outcomes

You will be able to

  • Build and use a channel for experimentation.
  • Describe the forces acting on a conker as it falls and rolls.
  • Observe and describe the effects of changing the channel surface.
  • Use a stopwatch to take readings and calculate speed.

You will need (per group of 4 to 5)

  • 1 x Jumbo Gratnells (F3) tray or several shallow Gratnells (F1) trays stacked to a similar height
  • 1 x Shallow Gratnells (F1) tray
  • 1 x Shallow Gratnells (F1) tray with a 30-section tray insert
  • 1 x Balance
  • 1 x 2-3m x 50cm piece of cardboard or a 2-3m length of square guttering
  • 1 x Roll of strong sticky tape
  • 1 x Piece of recycled bubble wrap the same dimensions as the bottom of the cardboard or guttering channel
  • 1 x Piece of recycled packing foam the same dimensions as the bottom of the cardboard or guttering channel
  • 30 x Conkers (can collect into a shallow Gratnells tray with 30-section insert in advance or as part of the activity)
  • 1 x Copy of the numbers 1-30 30-section tray insert printable
  • 1 x Scissors
  • 2 x Small ball of blue tack
  • 1 x Stopwatch
  • 1 x Notepad and pen or a device for recording your data


  • Fold the cardboard along its longest length into three equal-sized sections, bend the two outer pieces up to a 90-degree angle and secure in place with tape to create a channel.
  • Place one end of the channel on the edge of the jumbo Gratnells tray, use the blue tack to secure in place and prevent slipping.
  • Place the other end of the channel into a shallow Gratnells tray, use the blue tack to secure in place and prevent slipping.
  • Print and cut out one copy of the numbers 1-30 30-section tray insert printable (laminate if preferred and to protect against inclement weather for future use).
  • Collect you conkers into a shallow Gratnells tray with 30-section insert.

What to do

Take a look at our Conker Rolling What’s In My Tray activity video on YouTube

  • Work as a team to collect at least 30 conkers from nearby Horse Chestnut trees during September, be sure to get a well-varied collection in terms of size and shape.
  • Organise your conkers into a shallow Gratnells tray with a 30-section insert.
  • Number each section using the numbers 1-30 30-section tray insert printable.
  • Weigh each conker on the balance and make a note of its weight and section number.
  • Formulate a hypothesis or make a prediction as to which conkers will roll the fastest.
  • Place conker number one at the top of the channel, make sure you have your stopwatch ready.
  • Let go of the conker and time how long it takes to travel from the top of the channel to the back wall of the bottom shallow Gratnells tray.
  • Discuss how many times you should repeat each reading and what the role of each team member will be, e.g. dropping the conker, timing the conker, collecting the conkers at the bottom and putting them back into the correct tray insert section, recording the timings, taking photographs/videos.
  • Repeat this activity for conkers 2 to 30, or split the conkers between teams if needed.
  • You may wish to photograph and video your activity to record how you carried out your investigation.
  • Plot a graph of your results, conker weight vs average time for each individual conker. Or, calculate the average speed of each conker (speed = distance ÷ time) and plot that against the weight instead. You should only collate the data from one team on to your graph because there may be experimental differences in each team’s tray and channel set up.
  • What can you conclude from your results? What does this mean for conkers in terms of seed dispersal?
  • Place a sheet of bubble wrap in the base of your channel and repeat your investigation using conkers 1 to 5. What do you notice? Why?
  • Place a sheet of packing foam in the base of your channel and repeat your investigation using conkers 1 to 5. What do you notice? Why?

What is happening

Keywords: Gravity, Friction.

Gravity is the force that ‘pushes’ everything to the ground. Gravity acts on the conkers and ‘pushes’ them down from the top of the channel to the bottom when released. The equipment can be used to create channels with different surfaces for the conkers to be tested on. This activity investigates the effect of both conker weight and the surface of the channel. The rougher and bumpier the channel surface the more friction will be generated and the slower the conker will roll (lower speed or velocity), the smoother the channel surface the less friction will be generated and the faster the egg will roll (higher speed or velocity). The heavier the conker the greater the effect of gravity and the faster the conker will roll (higher speed or velocity) and vice versa. What is speed? Speed = Distance ÷ Time and can be calculated from your readings if you know the length of your channel including the distance to the back wall of the shallow tray. What is the velocity? Velocity is simply speeding with a direction. The force of gravity acts on the conker travelling down the guttering to create velocity. The velocity generated by the conker as it rolls down the slope provides the momentum required to carry the conker over the flat surface of the tray until it hits the back wall of the shallow tray and stops. Momentum doubles as velocity doubles.

Conkers are seeds from the Horse Chestnut tree. Their primary method of dispersal is by ‘popping’ or gently exploding out of their spikey casing and falling (due to the force of gravity) to the ground. You will find many conker cases and conkers dispersed under the canopy of a Horse Chestnut tree. The conkers then rely on a secondary method of dispersal, rolling, to travel even further away from their parent tree. It is advantageous for seeds to germinate away from the parent tree to reduce the competition for sunlight and nutrients. However, the conditions near the parent tree are already proven to be favourable for growth so travelling too far away only increases the risk of landing somewhere with unfavourable conditions. Horse Chestnut trees have evolved to disperse their seeds over an optimal distance. What other things could influence or interfere with the tree’s normal dispersal pattern?

Other things to try

  • To simplify:
    • Reduce the number of conkers tested
    • Reduce the number of repeats
    • Increase the length of the channel or use the packing foam-lined channel as the starter channel to make the conker roll more slowly, making timing using a stopwatch easier.
    • Dispense with the stopwatch and make conclusions based on observations alone.
  • To increase the challenge:
    • Select the number of conkers and repeats to suit interest/attention span.
    • Results could be recorded directly into a spreadsheet (i.e. using a rugged tablet device if working outdoors)
    • Speed could be calculated within the same spreadsheet and a graph plotted immediately.
    • Discuss the limitations of the approach, how many repeats are needed? Is it possible to discern a pattern when faced with natural variations in conker shapes and within the limit of the experimental design?
  • What other materials could you use to line the channel? Is there a way to make the conkers roll faster?
  • Try a slow-motion video to capture the rolling conkers or use video to more accurately measure the duration of travel.
  • Apps such as Playground Physics (free) or Vernier Video Physics could be used to capture your experiments and accurately record speed.
  • Find an isolated (no other Horse Chestnut trees nearby) and undisturbed Horse Chestnut tree with lots of fallen conkers and conker casings, map the canopy spread on square paper and record the location of all fallen conkers on the same map. How far away was the furthest conker from the tree trunk? Compare the features (weight, shape, size) of conkers found close to the tree trunk to those far away. Can you identify any patterns?
  • Share your photographs of your conker collection, experimental setup and videos on social media using #WhatsInMyTray and tag @Gratnells

Health and Safety

As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations.