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Moving Shadows

Moving Shadows

How do shadows change during the day?

  • A small toy
  • Paper
  • Coloured pencils
  • A clock

How to do it

Note: You will need to do this activity on a sunny day. You will need to return to it throughout the day.

  1. Begin the activity at the start of the morning. Find an open space in full sunlight and lay a piece of paper on the ground. Then place the toy in the middle of the piece of paper so that it stands up vertically.
  2. Take note of where the shadow of the toy falls by drawing around its outline using a coloured pencil. Label the outline with the time that you have drawn the shadow.
  3. Return each hour to check the position that the shadow from the toy has been cast in, drawing around it and labelling the drawing with the time. You could use a different coloured pencil for each shadow outline to help them stand out clearly.

What are we learning

Light travels in a straight line. When we place an object in its path, in this case a small toy, it blocks some of the light, creating a shadow. As the earth rotates, the position of the sun in the sky changes, which changes the length and position of shadows. In the morning the sun rises in the east, and the shadow is longer and cast west. By midday the sun is directly overhead, making the shadow short. In the afternoon the sun is setting in the west and the shadow grows longer again and cast east.

Investigate

A sundial is a device that uses the sun to tell the time. Find out more about how they have been used by many civilizations in history.

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Measure Scavenger Hunt

 Measure Scavenger Hunt

What different sizes can we find in the natural environment? 

  • A measuring tape or ruler
  • Scavenger hunt list (see example in photo)
  • A pencil or pen
  • A timer
  • A camera (optional))

How to do it

Note: you will need to prepare the scavenger hunt list in advance. Younger children could measure items in cm’s while older children could have a mixture of cm’s and mm’s.

  1. Take a copy of the measure scavenger hunt list and decide on an outdoor area that your hunt will take place in (for example, a garden, park or woodland).
  2. You have 15 minutes to find and photograph an example of each item on the list. You will need to use the measuring tape carefully to make sure you have found an accurate example of each item on the list.
  3. When the time is up, review the findings and count how many items you photographed.

Optional: Make this into a competitive team challenge and see who can find the most items. Alternatively, try going to a different natural environment to see if you can beat your score.

What are we learning

Measuring tapes help us to accurately measure the length and width of different objects. We have been using the metric system, in which length is measured in millimetres (mm), centimetres (cm), metres (m) or kilometres (km). There are ten millimetres in each centimetre. The natural world is full of many different sizes and shapes. Leaves from the same tree or plant can vary in appearance and size. However, they will always roughly correspond to the same basic shape.

Investigate

Choose your favourite leaf or flower from the scavenger hunt and find out what species it is. You could use a nature book to identify it or use an app such as ‘PlantSnap’.

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Frozen Fireworks

Frozen Fireworks

What happens when we mix fluids of different densities? 

You will need

  • A clear glass or jar
  • Warm water
  • Vegetable oil
  • Food colouring
  • An ice cube tray
  • A pipette (optional)
  • Honey and milk (optional)

How to do it

Note: you will need to prepare the ice cubes in advance of the activity.

  1. Fill up an ice cube tray with water. Add a few drops of food colouring to each ice cube mould, either by squeezing them from the bottle or using a pipette. Then place the tray in the freezer for a few hours.
  2. Once the ice cubes are frozen, part-fill your jar with warm water, leaving space at the top.
  3. Then add a 2cm layer of vegetable oil. You will notice that the oil floats on top of the water.
  4. Place the ice cubes into the jar and watch them float in the oil layer.
  5. Watch as the ice melts and the coloured droplets sink down into the water and mix together, creating fireworks!

What are we learning

Density is the mass of an object divided by its volume. Put another way, it is the amount of ‘stuff’ that can fit in a given space. Some materials are very light for their size while others are very heavy. For example, a brick and a sponge might be a similar size but the sponge would be a lot lighter. This is because it is less dense. Oil is less dense than water so it floats to the top of the jar. The ice cubes are also less dense than the water, which is why they float in the oil layer. As the ice melts and turns into liquid, it becomes denser than the oil. This causes the food colouring droplets to sink into the water and diffuse (spread out), creating what looks like fireworks.

Investigate

Now try adding other fluids to your jar, such as honey or milk. How do their densities compare to water and vegetable oil?

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Water Xylophones

Water Xylophones

You will need

  • Glass bottles
  • Water
  • A stick
  • A measuring jug (optional)

How to do it

  1. The challenge is to play a tune on a water xylophone, created from glass bottles.
  2. To produce a different pitch (sound frequency), each glass bottle should be filled with a different amount of water.
  3. Measure out the water and experiment with making different sounds by gently tapping the side of each bottle using a stick.
  4. Order the bottles from lowest to highest pitched. Then perform a tune on your musical instrument. What do you notice about the pitch of the sound and the volume of water in each bottle?

What are we learning

Musical instruments create sound waves, which are temporary compressions in the air. These sounds are made when objects vibrate. When we tap each xylophone bottle we cause the glass to vibrate. These disturbances travel through space and ultimately make your eardrum vibrate, to be heard as sounds. This vibration produces a higher pitched sound when there is less water in the bottle. They produce a lower pitched sound when there is more water in the bottle. If you have used an assortment of different sized or shaped bottles then you may have noticed that you can fill two bottles with the same amount of water and still create different sounds. This is because the sound is vibrating within a different space.

Investigate

Ancient mathematicians like Pythagoras investigated the mathematics of musical scales. Can you find out more about this?

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Robotic Arm

Robotic Arm

You will need

  • Thick cardboard
  • Split pins
  • A sharp pencil
  • A ruler and scissors
  • An elastic band
  • String

How to do it

  1. Cut out two identical rectangular strips of 10cm length out of cardboard. Then cut out two identical cardboard ‘grabber’ arms.
  2. Use a sharp pencil to pierce a small hole in either end of each cardboard strip.
  3. Attach the two rectangular strips together at one end using a split pin. Join the opposite ends to the grabber arms, positioning the grabber hands pointing outwards.
  4. Pull the two grabber arms together so they overlap and join them together with a split pin. Your grabber hands should now be pointing inwards towards each other.
  5. Cut a longer strip of cardboard to act as a handle. Pierce a hole in one end and attach it to the split pin used to overlap the grabber arms.
  6. Attach an elastic band between the two spilt pins at either end of the arm.
  7. Tie a short piece of string to the bottom of the elastic band. Hold the handle and gently pull the string back and forth to open and close the arm. Can you pick up a small object with it?

What are we learning

Robotic arms are a classic use of robotic technology, and can be found on factory production lines, controlled by computers. They have a variety of uses. They can do jobs that are very repetitive for humans such as screwing the lids on jars on a production line in a factory. They can do jobs that are difficult for humans such as putting small parts (such as bolts) onto a car in precisely the right place. They can also do jobs that are dangerous for humans such as moving hazardous materials. Sometimes robotic arms are found on a much larger robot, other times they are a standalone arm. Increasingly, roboticists consider using innovative soft materials (‘soft robotics’) for grippers at the end of the arms. Such ‘smart’ materials include shape-memory polymers (SMPs) that can temporarily deform and then return to their original shape.

Investigate

The Curiosity Rover on the planet Mars uses a robotic arm. Find out more about this.

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Tilting Marble Maze

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Tilting Marble Maze

You will need

  • A shoebox lid
  • Lolly sticks or strips of thick cardboard
  • Sticky tape
  • Scissors
  • A marble

How to do it

Fill the pipette or syringe with water. Then carefully add drops of water to the raindrop outline. How many drops of water can the raindrop hold before the water spills over the edge?

Repeat the activity on a raindrop of a different size or shape.

  1. Position the shoebox lid in front of you so that the inner part of the box is facing upwards.
  2. Begin to arrange the lolly sticks or cardboard strips to create the marble maze ramps and bumpers. You could vary the length of them to add variety to your marble maze.
  3. Attach the first lolly sticks or cardboard strip using sticky tape. Position each so that it is tilting downwards slightly.
  4. Continue to attach the marble maze pieces down the length of the shoebox. Vary the angles of each to create different speeds of travel.
  5. Check how well the marble maze is working as you go and make any adjustments needed to help the marble travel downwards through the ramps.
  6. Test your marble maze by tilting the shoebox with your hands to navigate the marble around the maze. Does it work?

What are we learning

Before the marble travels down the maze, it has potential energy from being lifted up to a height. As it rolls along the angled ramps, this converts into kinetic (movement) energy. Gravity is the force pulling the marble to the ground.

It would take it straight down if not for the angled runways, which instead guide the marble down and sideways. As the marble rubs against the cardboard it also creates an opposing force called friction. This slows down the marble. Angles are critical to the marble run’s success. The greater the angle, the quicker the marble will roll.

Investigate

Now create a marble maze by positioning the maze walls using only vertical and horizontal lines instead of tilting downwards. Is it easier or harder to navigate a maze like this?

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Falling Raindrops

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Falling Raindrops

What holds raindrops together?

  • A pipette or syringe
  • Water
  • A piece of A4 paper
  • A pen
  • A plastic wallet

How to do it

Fill the pipette or syringe with water. Then carefully add drops of water to the raindrop outline. How many drops of water can the raindrop hold before the water spills over the edge?

Repeat the activity on a raindrop of a different size or shape.

  1. Begin by drawing outlines of raindrops onto a piece of paper. Try to vary the size and shape of each raindrop.
  2. Place the paper inside a plastic wallet and position it on a flat surface. The plastic wallet helps to protect the paper from getting smudged or damaged as you add the water.
  3. Fill the pipette or syringe with water. Then carefully add drops of water to the raindrop outline. How many drops of water can the raindrop hold before the water spills over the edge? 
  4. Repeat the activity on a raindrop of a different size or shape.

What are we learning

As we add more drops of water onto the raindrop we see a dome shape forming. The water molecules are attracted to each other and make a single large drop. At the same time, a property called surface tension tries to minimise the surface area of the water, making the curve shape. This also prevents the water from spilling out. However, as we add more drops, the gravitational pull on the weight of the water eventually becomes more powerful than the surface tension, causing the water to spill.

As raindrops fall from the sky they begin their journey as a sphere shape. As they fall to the ground, the force of gravity pulls them downwards. The force of air resistance pushes up against them, flattening the bottom of the raindrop.

Investigate

Repeat this activity on a penny coin. Which side holds the most drops of water, heads or tails?

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