Video transcript of Episode 6: Milk Carton Sprinkler
On-screen text reads: “Do Try This at Home from the Institute of Physics. Episode 6: Milk Carton Sprinkler.”
Camera cuts to an outdoor courtyard. We hear some guitar music playing in the background. There is an outdoor plant on a wooden table and the camera tilts upwards to show a drinks carton suspended above the plant. The carton has holes in the bottom which allows the water inside to escape. We can hear Melissa say: “And hold it over your plants to water them!”
Camera cuts back to Melissa who is sitting in her living room and is ready to present the experiment.
Melissa: "Hello and welcome to Do Try This at Home, brought to you by the Institute of Physics. We’re making these videos because we want to help parents and carers in the UK and Ireland get their kids excited and curious about the world around them even when you can’t leave the house. My name’s Melissa and welcome to my living room!
"Now even with our famous British rain sometimes my plants need a little bit of extra help, but I don’t own a water sprinkler, so I’ve come up with an invention: The Milk Carton Water Sprinkler!"
Melissa picks up an empty 1 litre drink carton and shows it to the camera. The cap has been removed from the spout. It is empty and a piece of string has been threaded through a hole at the top of it. We hear a piano play a few celebratory notes.
We hear a swishing sound as the camera initially shows Melissa in profile. She is no longer holding the carton. The noise and change of angle tell us that the scene has moved on.
Melissa: "To make your own Milk Carton Sprinkler you’ll need a piece of string, the length of the string is entirely up to you, an empty carton, it could be a milk or a juice carton, whatever you have to hand, a pair of scissors and a bowl. Any type of bowl that you have will work just as well be it a washing up bowl or even a bucket."
As she speaks, Melissa shows the different household items needed for the experiment.
Melissa: "So, with this next part be very careful when doing this with family members because we’re going to be using our scissors as a stabbing tool to create our holes, coupled by the double whammy that we’re going to get water absolutely everywhere. So, I do recommend you carry out the experiment either in the kitchen or somewhere outdoors.
"What I did earlier was make a hole in the bottom left corner of each side of the carton like this."
Camera cuts to a close-up shot of the drink carton. We can see that there’s a hole in the bottom left corner of each side of the carton. To demonstrate how she made each hole she carefully pokes one of the scissor blades into each hole and rotates it to make a circular hole.
Melissa: "Next, at the top of your flap create another hole. Then, get your string and thread it through the hole and then tie a knot. And there you have it."
As she’s speaking, Melissa holds the top part of the carton flat whilst she pokes a hole through the flap at the top of the carton. She then threads the string through the hole and ties it into a knot so that she can hang it the carton up.
Melissa: "So, grab your carton and your bowl, fill it up with water and then head out to your designated sprinkler zone."
Pour the water in and watch it spin.”
Melissa places the carton on top of the bowl, and then we hear a swishing sound, and the camera cuts to a close-up shot of the drink carton sitting upright in a large mixing bowl. We are outside and Melissa is pouring some water from a jug into the carton via the pouring spout. Melissa lifts the carton and holds it over the courtyard floor. As she does this, the water squirts out of the holes at the bottom and the carton spins.
Camera then cuts to the original image of the carton suspended above a plant. Melissa can be heard saying: "And hold it over your plants to water them."
Camera switches back to a medium shot of Melissa in her living room.
Melissa: "So, what’s going on there and how can you explain it to your family? At the bottom where I’ve made my holes the water is under pressure. The water above is pressing down on the water below and this creates a force that pushes the water out of our holes, which is good for my plants."
As Melissa speaks, she points to the holes at the bottom of the carton and shows, using a downward motion with her hand, the direction of the force caused by the water pressing down.
The camera then cuts to a birds-eye view of the carton.
Melissa: "Now let’s get to the bottom of why it spins. Looking at the milk carton from above with the string in the middle when you make a hole the water comes out here which causes a pushing force on the opposite side of the carton here."
Melissa lifts the carton away and we see a square of stiff material which represents the bottom of the carton. We are looking at the bottom of the carton from above. In the middle of the bottom of the carton is a pin. Melissa points to the location of one of the holes in the top left corner. A line appears showing that water is pushed out from this point. She then points the opposite corner, and an arrow appears next to her finger and points away from her finger to show the pushing force on the carton.
Melissa: "Now it’s important that the holes are in the corner not the middle. If I push here and here nothing happens. By making the pushing forces off-centre the carton spins around the string in the middle."
Melissa places one finger in the middle of one of the sides of the carton bottom, and another directly below it on the other side. She tries to push with both fingers, but nothing happens. She then places one finger at the top right corner and another in the bottom left corner. As she pushes, the bottom of the carton spins around the pin like a wheel.
Melissa: "There are four streams of water coming out of our carton in four different directions. The result is that there are four forces on our carton pushing it around which causes it to spin."
As she speaks, four lines appear from four corners of the bottom of the carton to show the water being released. These lines are replaced by four arrows representing the pushing force, the arrows appear from the corner that is directly opposite the hole, and each one points away from the carton.
Camera cuts back to a medium shot of Melissa.
Melissa: "If you’re not completely sure about the science don’t worry. As always test it out, have fun together and then you can look it up together later on if you need to. Thanks for watching and see you next time!”
The image fades to be replaced by some on-screen text which reads: “Do Try This at Home from the Institute of Physics. For instructions and more Do Try This at Home films visit iop.org/athome. These experiments have not been specifically safety tested for home use, but we believe them to be safe if the instructions are followed. Adult supervision is recommended as appropriate. All experiments are carried out at your own risk."