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The science behind ziplines
Ask the group if anyone knows how or why ziplines work. Let a few people respond.
Explain that gravity is the key factor as to how and why zip lines work. The gravity and weight of the objects travelling helps to pull them from a high point to a low point. Gravity is the same invisible force that keeps us on Earth.  
See if anyone knows what may need to be considered when building a new zipline.
Tell everyone that when creating a zip wire, we must consider the following how fast it will we go, how the items will be attached to the rope, what route the zipline will follow and how the cables will be secured.
Explain that we know gravity plays a big part in making ziplines work, but ask what else might be a key factor. Let a few people share their ideas.
Explain that the mass of the item, air resistance, the slope of the line and the length of the line, and friction all impact on how well a zipline will work.
Tell everyone that the mass of the item on the line (the weight of the objects) affects the zipline as the heavier it is, the faster it’ll travel. Air resistance’s a factor, as the bigger an object the more air resistance it’ll have. The slope of the line is important, as the steeper the line, the higher the velocity and the faster it’ll go. The length of line is important, because the longer the line is, the more time you’ll have to achieve maximum speed. Finally, friction, is key, especially for the pulley, as the better your pulley is, the less friction it’ll create and the faster it’ll go.

Resources

String
Scissors
Thick card
Glue
Ruler
Paper drinking straws
Paper cups
Thread
Stopwatches or timers
Pens
Paper
Items to use as weights, such as toys, teddies or marbles
Clothes hangers (optional)
Paper clips (optional)
An umbrella with a hook handle (optional)

Instructions

Before you begin
Use the safety checklist to help you plan and risk assess your activity. Additional help to carry out your risk assessment, including examples can be found here. Don’t forget to make sure all young people and adults involved in the activity know how to take part safely.
Make sure you’ll have enough adult helpers. You may need some parents and carers to help if you’re short on helpers
Discovering ziplines
Gather everyone in a group.
Ask if anyone has seen or been on a zipline, or if anyone knows what one is. Let a few people answer.
Tell everyone that, in its simplest form, a zip line usually consists of a rope stretched between two points of differing heights. They are used to transport people or objects down the rope, using a pulley.  
See if anyone knows why humans have used ziplines. Explain that in the past, and still now, zip lines have been used for practical purposes. They’ve helped people to transport themselves and goods across difficult terrain or rivers. In Australia, ziplines were once used zip lines to transport necessities to people across entire valleys.
Tell people that today, in mountainous places, such as Bolivia, Nepal and India, they use a system of zip-lines to transport harvested crops across wide, vast valleys. 
Tell everyone that some ziplines have been created for fun and to explore new places, too. One zipline used for exploring was created by Dr. Donald Perry and it allowed him to travel across the rainforest canopy in Costa Rica in the 1970’s. It still exists today. There’s also ziplines to explore snowy Alpine peaks of the Italian Dolomites and Table Mountain in Cape Town, South Africa.
The science behind ziplines
Ask the group if anyone knows how or why ziplines work. Let a few people respond.
Explain that gravity is the key factor as to how and why zip lines work. The gravity and weight of the objects travelling helps to pull them from a high point to a low point. Gravity is the same invisible force that keeps us on Earth.  
See if anyone knows what may need to be considered when building a new zipline.
Tell everyone that when creating a zip wire, we must consider the following how fast it will we go, how the items will be attached to the rope, what route the zipline will follow and how the cables will be secured.
Explain that we know gravity plays a big part in making ziplines work, but ask what else might be a key factor. Let a few people share their ideas.
Explain that the mass of the item, air resistance, the slope of the line and the length of the line, and friction all impact on how well a zipline will work.
Tell everyone that the mass of the item on the line (the weight of the objects) affects the zipline as the heavier it is, the faster it’ll travel. Air resistance’s a factor, as the bigger an object the more air resistance it’ll have. The slope of the line is important, as the steeper the line, the higher the velocity and the faster it’ll go. The length of line is important, because the longer the line is, the more time you’ll have to achieve maximum speed. Finally, friction, is key, especially for the pulley, as the better your pulley is, the less friction it’ll create and the faster it’ll go.
Making a zipline
Gather everyone together in a circle, if not already in one, and explain that they’re going to make, test and experiment with their own zipline.
Everyone should get into pairs or small groups.
Cut a piece of string, which is several metres long. You could create on zipline for the whole group to use or a few ziplines for groups to share. A responsible adult will need to secure one end of the string to something relatively high and one end slightly lower to create a zipline. You should carefully think about what you’ll use, such as two tables of differing heights, and plan how you might do this. Remember, young people will need to use the ziplines to test their creations, and you’ll need to remind everyone of the string as a trip or collision hazard.
People will need to thread on the pulley to the string, so the lower end of the zipline could be loosely tied, to allow people to remove the string easily and add their pulley. 
Creating a pulley
Each group should take a straw and cut it to around 10cm in length.
Next, each group should carefully cut out two card circles, around 3cm in diameter.
Everyone should carefully create a hole in the middle of each card circle, just smaller than the diameter of the straw.
They should then thread these pieces of card onto the middle of the straw leaving a gap between them just wider than the width of the string you’re using as the zipline.
This is your pulley!
Creating a travel system
Carefully poke two holes opposite each other in the side of your cups, about a third of the way down.  
Next, loop a piece of thread through these holes. The thread should then be passed through the straw used in the pulley.
Tie the two ends of the thread together, so that the straw is close to the top of the cup. This’ll prevent the string falling off later.
Time to test it!
1. Now everyone’s made their zipline, they should test it.

2. The group should carefully untie one end of the zipline, then carefully thread their pulley and cup system onto the string. Remember, people will need to thread on the pulley to the string after it’s made, so the lower end of the zipline could be loosely tied, to allow people to remove the string easily and add their pulley. 

3. When it’s on, or a responsible adult depending on the height and location of the zipline, should take their pulley and cup to the top of the zipline.

4. They’ll need to record how long it takes for the item to travel down the zipline, using a stopwatch or timer. They could note this down on a piece of paper as the first attempt.

5. When they’re ready, they’ll need to let go of their creation and watch it fly!

6. After the first attempt, let people experiment to try and make their cup go faster. Some suggestions are:

Adjusting the angle, by moving the lower end of the string higher or lower 
Adjusting the weight, by adding objects into or taking objects from your cup 
Adjust the length, by increasing or decreasing the length of your string 
Adjust the tension, by pulling the string tight or loosening it
Adjust the air resistance, by sellotaping some paper sails to the cup 
7. You could also let people test out different types of pulleys. They could do this by using other objects, such as an umbrella with a hook handle and placing items inside, using a coat hanger with a hook, or using a paperclip. You could perhaps give different groups, different items to try.

Reflection
This activity will hopefully have helped you to learn about the uses of ziplines and how different factors affect the speed of your zipline.

How did everyone find making the pulley and zipline? How was your first attempt, and how did you make the zipline go faster?

Can anyone remember what the factors are that affect the speed of the zipline are?

They’re gravity, friction, air resistance, mass (or weight), slope and the length of the line.

Did you find changing any of these factors helped to make the zipline faster? Did anything make the zipline go slower than your first attempt? What was the fastest time you achieved?

If you were going to do this activity again, what would you do differently? And how well did you work in your pair or as a team, so everyone had a chance to build the pulley, release the cup on the zipline, time or record the attempt and think of ideas to make it go faster? Did everyone have their voice heard and be able to contribute?

If you experimented with different items as the pulley, did any items work better as a pulley system? Why do you think some items worked better, or even worked worse?

You now know the principles of building a zip wire, so when you next have a chance to go on a zip wire think about how or why you can go faster.

Safety
All activities must be safely managed. Use the safety checklist to help you plan and risk assess your activity. Do a risk assessment and take appropriate steps to reduce risk. Always get approval for the activity and have suitable supervision and an InTouch process.

Scissors
Supervise young people appropriately when they’re using scissors. Store all sharp objects securely, out of the reach of young people.

Glue and solvents
Supervise young people appropriately when they’re using glue and solvent products. Make sure there’s plenty of ventilation. Be aware of any medical conditions which could be affected by glue or solvent use and make adjustments as needed.

When the zip wire is up, take precautions to ensure no one walks into the zip wire  
Plan carefully how you will get up high to do this.

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