Tag Archives: physics

STEM Students answer Children’s Questions #5

When visiting schools and museums our Street Scientists often get asked a variety of questions from curious children. Here are the answers to some of our favourite questions!

This week, we’re answering questions on Engineering!

How do rockets get so much power to shoot into space?

-asked by Lea, 8, from West Jesmond Primary

Rockets are not too different from regular planes and cars – they all need something called ‘fuel’. The only difference is that rockets need a (lot of) special fuel to allow them to take off. The fuel is burned inside the bottom of the rocket which produces a hot gas (called an exhaust gas). This hot gas is pushed out the bottom of the rocket through something called a ‘nozzle’ (a tube that gets smaller closer to the exit) which makes the gas travel faster (acceleration). It’s this acceleration of the gas that’s used to push the rocket off the ground. Rocket fuel is special as it produces lots of energy compared to regular fuel – the same way some foods give us more energy than others (like chocolate!)
– Jenny, Mechanical Engineering Student

Why are triangles the strongest shape to build lots of bridges?

-asked by Rosie, 10, from Ravenswood Primary School

Shapes that have straight sides are called ‘polygons’. Triangles are special because out of all the polygons, they have the least number of sides. Because triangles only have three straight sides, they are harder to squash than other shapes, for example: squares. If you look at the picture below, you can see how applying a force to a square would make it deform (squash), whereas no matter how you apply force to a triangle, this can’t happen because each side supports each other, which is why triangles are so strong! This is why engineers use triangles in their designs, to make their bridges as strong as possible.
-Jenny, Mechanical Engineering student

How was electricity made?

-asked by Emily, 7, from Simonside Primary School

When we refer to electricity, we mean the movement of tiny particles called electrons through a material that will allow them to pass through called a conducting material. An example of a conducting material is a copper wire which we usually see covered by rubber – if you have a charger for a tablet or phone then that is a great example.

To generate electricity, you usually need a fuel source. This could be in the form of coal or gas and nowadays hydropower and wind are becoming increasingly common sources of fuel. Electricity is generated through a machine called a generator which takes one form of energy and converts it into electrical energy. A common visual example would be a wind turbine. You can often find these in large empty fields or sometimes when you go to the beach you can see wind turbines far out in the ocean. Wind causes the blades of the turbine to spin which means magnets inside the wind turbine will also spin. These magnets are surrounded by copper wires which allow electrons to flow through them when the magnets spin around them and this flow of electrons is what generates electricity.
– Sidra, Mechanical Engineering Student

How do TVs and computers work?

-asked by Yedam, 8, from West Jesmond Primary School

Computers and other electronic devices like TVs, phones and tablets all work in a similar way – they take instructions in the form of ‘code’ – code is just a language that computers can understand. These coded instructions are called ‘programming’. A computer scientist ‘programs’ a computer to work before we buy it so it can recognise our instructions – this is the computer’s ‘software’. When we give our computer an instruction (such as turning it on, clicking the mouse or going onto the internet) the ‘software’ tells the physical parts (the ‘hardware’) what to do.
– Jenny, Mechanical Engineering Student

If you have any questions that you would like our team to answer, please leave a comment below!

Space Day: Structure of the Planets

This year for Space Day, Earth Science student, Jade, explains all about the structure of the sun, moon and the planets in the solar system.

The Sun

  • The sun isn’t a planet, it’s a star in the Yellow Dwarf stage of its life.
  • The sun is in the middle of the solar system and is a ball of hot gases (mostly helium).
  • Even though it is made of gases it still has 6 layers within it:
    • Core – Where solar energy is generated which is where the heat comes from.
    • Radioactive zone
    • Convection zone – Where the heat travels up to the surface.
    • Photosphere – Visible surface
    • Chromosphere – Thin layer of gas
    • Corona – Thick atmosphere extending for millions of miles and it’s only visible during a solar eclipse


  • Mercury is the smallest planet in the solar system.
  • It experiences extreme temperatures, both hot and cold. The heat is from being so close to the sun and the cold is due to the lack of atmosphere which causes the heat to escape.
  • Mercury’s interior is made up of a solid inner core, liquid middle core and a solid layer of iron sulphides. Then there is a mantle and a crust which together are around 400km thick at and mostly made from silicate minerals.
  • On the surface it has craters from meteorite impacts and lava plains from past volcanism that ended around 750 million years ago.
  • Although it has extreme heat there is ice at the poles, even during the heat as the ice is in the shadows of craters.


  • Second closet planet to the sun.
  • It has an iron core, a rocky mantle and a thin crust, similar to Earth.
  • As the rocky mantle moves underneath the crust it bulges and forms mountains and volcanoes.
  • There isn’t any water on Venus due to its high temperature.
  • It has an atmosphere mostly made up of Carbon Dioxide, but it doesn’t have any wind due to its slow rotation.
  • It can sometimes rain sulfuric acid.


  • Solid inner core made of iron and nickel.
  • Liquid outer core also made out of iron and nickel.
  • Rocky mantle which is mostly a fluid which convects heat from the core to the surface. As it convects, it forces the plates of the crust to move around forming mountains and volcanoes as they collide or move away from each other.
  • The crust made up mostly of silicon and oxygen (the crust is thinner under the ocean than the rest of the crust).

The Moon

  • Similar to Earth in composition but no longer has volcanism as there are no plate tectonics.
  • The composition is so similar because they were made from the collision between a small planet and the Earth and the moon was the bit left over.


  • Mars has a solid inner core made of dense iron, nickel and sulphur.
  • It has a rocky mantle and a crust mostly made of iron, magnesium and aluminium.
  • Previously it had tectonics which formed volcanoes and the largest canyon in the solar system (Valles Marineris).
  •  It also has similar sedimentary processes to Earth such as dunes.


  • One of the gas giants mainly made up of hydrogen and helium.
  • Structure similar to the sun. It is unclear what the core of Jupiter is made up of, but it is surrounded by metallic hydrogen formed when the hydrogen is under so much pressure that the electrons are squeezed off making it electrically conductive like metal. The upper layers of Jupiter are then more hydrogen either as a liquid or gas (the high pressure and high temperature makes the hydrogen a liquid).
  • Jupiter spins so fast that it generates a magnetic field.
  • It has 63 moons, one of which is Europa:

Europa (a moon of Jupiter)

Europa has an iron core, a rocky mantle, an ocean of salty water, and a lot of ice.  


  • Another gas giant mostly made of helium and hydrogen.
  • Saturn’s core is made up of dense metals like iron and nickel and some rocky material.
  • Saturn’s density is less than water which means it could theoretically float on a giant mass of water.
  • Saturn is the only one of the gas giants with visible rings as the rings are mostly made of ice which reflects the light well.


  • This ice giant rotates at nearly 90o from the plane of its orbit, which makes it look like it’s spinning on its side.
  • The icy mantle surrounding the small rocky core is made up of dense water, methane and ammonia.
  • The atmosphere is made up of methane gas which give Uranus it’s blue-green colour.
  • It’s bigger than Neptune but it has a smaller mass.
  • It has 27 moons.


  • Neptune is shrinking and releasing heat.
  • It has a similar structure to Uranus as its mostly made up of icy materials made of dense water, methane and ammonia fluids around a small rocky core.
  • It’s atmosphere is mostly made form hydrogen, helium, and methane and it doesn’t have a solid surface (similar to all of the gas giants.)
  • It has 14 moons.

International Asteroid Day!

What is an asteroid?

You may be wondering what the difference is between an asteroid, meteor, meteorite and every other name given to a shooting star or flying clump of rock in space. Well we have broken it down into an answer that is simple….. Sort of. It all starts with an asteroid.

An asteroid is a large rocky (planet looking) body, in orbit of the sun, that is too small to be classified as a planet. In space there are millions of asteroids and lots of them are a potential threat to Earth. Asteroids range in size from hundreds of miles to several feet in diameter.

A meteoroid is a particle of an meteoroid that has broken off and is now orbiting the sun. If a meteoroid enters the Earth’s atmosphere it is then known as a meteor. A meteor shower is a group of meteoroids all travelling in parallel trajectories from one point in space. Most meteors burn up when they are travelling through our atmosphere and therefore never hit the earth’s surface. The meteors that do hit earth are called meteorites.

Asteroid defence?

Over the past 4.5 billion years since the Earth was formed, about 4.5 billion meteors (the sizes of cars) have made their way through its atmosphere. Yes, that’s around one automobile sized meteor every year. Although, these are meteors and not meteorites, therefore they create a substantial fireball but burn out before hitting the ground.

Scientists these days are able to tell if an asteroid or meteor is en route to earth 30-40 years before it does. This is enough time for us to destroy it before it destroys us. We can do this by exploding the asteroid or meteor, although sometimes we can divert them away from earth instead.

When is the next meteor shower?

Unfortunately you will have to wait a couple months for our next meteor shower, it is called Perseid and will be peaking in our skies on the 12- 13th of August. In order to get the most out of your meteor shower view, we recommend getting out into the middle of nowhere where there is little to no light pollution; bringing a friend or your family and a warm blanket (also a telescope if you’ve got one). Once you’re comfortable, sit tight and wait for the spectacular starry show!

Visit asteroidday.org to find out more.










Physics, forces and flipping

Ever wondered what makes the perfect pancake flip? Let’s look at the physics behind getting those pancakes flying through the air.

If we start with our pancake at rest in the pan, the pancake will not move unless a force is put upon it. This is Newton’s first law of motion, an object at rest will remain at rest unless acted on by an outside force. In order to launch our pancake in the air we therefore apply a force to it. We can use an energy equation to work out the velocity (speed with a direction) needed to launch the pancake into the air as follows:

m – Mass of the pancake

g – Gravitational field of the earth 9.81 metres per second

h – Height of pancake flip

 v – Launch velocity

We now need Newton’s second law of motion to find out how fast we need to flip the pancake. Newton’s second law of motion states that a force, acting on an object, will change its velocity by changing either its speed and/or its direction. In the case of our pancake the flipping force will increase the velocity and send the pancake in an upwards direction. The energy equation can be rearrange to give the pancake launch velocity:

If we want to flip the pancake 1 metre in the air we need a launch velocity of 4.4 metres per second. If our launch velocity is over 6 metres per second however, our pancake will get stuck to the ceiling! We also have to be fast to catch the pancake as it falls back down or we could be left with pancake on the floor! For a flip of 1 metre we only have 0.9 of a second to catch our pancake. We can calculate the air time (t) of our pancake using the following equation:So when you are flipping your pancakes today think of all the wonderful physics behind that perfect flip!

The Science of Santa

We all know Father Christmas is one of the most wonderful and magical parts of Christmas, so we thought we’d use our scientific knowledge to work out how the fastest man in the universe delivers all those presents in one night!

There are approximately 2 billion children in the world. Of those, about 700,000,000 celebrate Christmas (and make the nice list!). With an average of three children per house, that’s a whopping 233,000,000 stops that Saint Nick has to make! Now bear with us…

If those stops are distributed evenly around the world, with a total surface area of 317,000,000 miles, each stop is 0.91 miles apart, making a total of 212,030,000 miles that Santa has to travel.

Because of the time differences across the globe, Santa has approximately 32 hours to complete his trip, maximising the night time (and sleeping children) available. Using speed = distance ÷ time, we can then work out that he has to travel at 6,650,807.72 mph! That’s about 1,800 miles per second.

So, remember to leave out a mince pie or two to help him along on this, his busiest of nights!

Sci-Fi vs Sci-Fact

It’s World Space Week, so naturally, we seized the opportunity to stick on our favourite sci-fi blockbusters. However, with our scientific minds always at work, we couldn’t rest easy without sharing with you those space movies that are more fiction than science…

Star Wars

Okay, so we appreciate this galactic fantasy series isn’t ever going to be exactly scientifically accurate, what with all the aliens, droids, space travel and the mystical “Force”. But those space battles that Star Wars is known for, featuring all kinds of explosions and blasts? Well, in reality, they would actually be silent. Sound waves travel via the vibration of atoms and molecules in a medium such as air. Space is a vacuum, devoid of all matter – including gases – meaning the sound vibrations wouldn’t work.


Even if it were feasible to land on an asteroid and drill into the centre of it (just in case you were wondering, it isn’t), the energy required to destroy this huge, Texas-sized, asteroid would amount to a LOT more than one nuclear bomb. The most powerful nuclear bomb ever detonated on earth, Big Ivan, has a total energy output of 418,000 terajoules. Leicester post-graduate students found that in order to split this asteroid in two, Bruce Willis would have had to detonate a bomb with 800 trillion terajoules of energy output.

The Martian

Ahh, a little respite from the scientific disaster that is Armageddon, The Martian is actually hailed as one of the most scientifically accurate sci-fi movies of all time. The main plot line (humans visiting Mars) looks to be scientifically feasible at some point in the future, and growing potatoes with a combination of your own excretion and Martian soil? Possible, apparently. However, whilst we’re willing to give credit where it’s due, this film is not without its inaccuracies.

The main scientific issue with this film is actually the driving force behind the whole plot – the sand storm that leaves Matt Damon’s character, Mark Watney, stranded on Mars. Whilst sand storms definitely do occur on Mars, the atmosphere is so thin compared to Earth’s that a 100mph wind on Mars would feel more like an 11mph wind does on Earth – making it unlikely to cause the destruction that sees Watney separated from his crew.


The astronauts in Interstellar make use of a wormhole next to Saturn, which enables them to travel from our galaxy to an entirely different galaxy in a short amount of time. According to Einstein’s theory of general relativity, wormholes are a possibility.

A wormhole is created by warping the fabric of space-time. If you think of space as a flat piece of paper, the distance is great between one end of the paper and the other. Bend the paper in half and the opposite ends of the paper are now much closer – punch a hole between the two ends of paper and you now have a tunnel which grants you instantaneous access between both ends, instead of travelling the long way from one end of the flat sheet of paper to the other.

However, astrophysicist Kip Thorne points out that in reality, there is a strong indication that wormholes through which humans could travel are forbidden by the laws of physics. Should we ever come across one, a wormhole is likely to be so unstable that the walls of it will collapse so fast that nothing is able to make it through.


A central plot point in this film depends on Clooney’s character, Matt Kowalski, whizzing from the Hubble Space Telescope to the International Space Station using his jet pack. However, Hubble orbits at an altitude of 559 kilometres whilst the ISS sits at 423 kilometres; the distance in orbit between the two makes travelling between them completely unfeasible (especially in a jet pack).

#TryThisTuesday: Rice Bottle

Our #TryThisTuesday this week, is a challenge for you. The task is to fill a dry bottle with rice and lift it up using only a pencil.

Have a go or challenge your friends, once you think you’ve cracked it (or given up) scroll down to see how we did it!

The Solution

Take the lid off the bottle and push the pencil half way into the rice. Take the pencil out again and push it back in, repeat this about 10 times. Eventually, when you pull the pencil to take it out, the bottle will lift up with it!

This occurs due to the force of friction acting on the pencil and holding it in place. When you first pour the rice into the bottle, it will arrange itself with lots of gaps but every time you insert the pencil you push the rice down making it more compact or dense. Some grains may even break or change shape under impact with your pencil. The more you do this, the greater the surface area of rice that comes into contact with the pencil. This gives a greater force of friction. Friction is a force of resistance between two objects when they  move past each other. The force is so strong at this point that it doesn’t allow the pencil to slip past the rice and so the rice (and the bottle) moves with the pencil as you lift it.

In the Real World…

This works in a similar way to quicksand. If you were to step onto quicksand, you would compact the particles, making them move closer together and lock around your foot, pulling you in. The friction makes it difficult for you to pull your foot out. Don’t worry too much though – quicksand is much denser than a human being so you wouldn’t be able to completely sink in it. As we learnt from our ketchup packet submarine and the oil and water experiment – less dense substances float above denser substances so you would stay above the surface of quicksand!

#TryThisTuesday: Bending Water

This week’s experiment is quick and simple but sure to amaze!

You will need:

  • A balloon
  • An indoor tap
  • Clean dry hair


  1. Turn the tap on so there is a very thin but constant stream of water flowing
  2. Rub the balloon on your hair until you form static (about 10 seconds, until your hair begins to stand on end)
  3. Slowly bring the balloon close to the flowing water while being careful not to actually touch the water
  4. Watch the water bend towards the balloon!


The Science

When you rub the balloon on your hair, tiny electrons are collected on the balloon. These electrons have a negative charge. This causes the balloon itself to have an overall negative charge, therefore it is attracted to things with a positive charge (opposites attract!). The flow of water has a positive charge, therefore the attraction is strong enough to pull the water towards the balloon.

This is known as static electricity!

Your Questions Answered!

As we have reached the end of the school year, here is a little round up of some of our favourite questions that children have asked us during STEM workshops.

1. Why doesn’t the energy ball give you an electric shock?

The energy ball is a little device we have that looks like a ping pong ball with two metal strips on top. Inside there is a light, a buzzer and a battery. If two people touch one metal strip each and then with their other hands touch each other, the ball lights up and buzzes. This works because we are conductors of electricity – electrons from the battery flow through us and back into the ball to complete the circuit.

The reason you don’t feel a shock when touching the energy ball because there isn’t enough electricity flowing through you to be able to feel it, and certainly not enough to harm you!

2. What do plants poo and wee? – St Wilfrids, Blyth

All living things have seven things in common – movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. The sixth one, excretion, is a scientific word for producing waste. In humans, and many animals, that is our poo and our wee. They are the leftover waste products that our body doesn’t need so gets rid of.

Plants are living things, just like us, but you may have noticed they don’t poo or wee like we do. Rather than eat food like us, they make their own through photosynthesis. This produces a waste gas called oxygen which we breath in. Plants excrete oxygen rather than poo or wee.

3. Why does the moon control the sea? – Grange First School

Gravity is the force that keeps us close to the Earth, all really big things like planets and stars have a gravitational pull that attracts things near by. Because the moon is so big and so close to Earth it has quite a strong gravitational pull on our planet. The moon causes the water in the oceans facing it to pull towards it, resulting in a high tide. The pull of the sun’s gravity and the Earth’s own gravity also have an effect on the tides.

4. I’m the only one who can touch their nose with their tongue, is that because of my genes? – St Marys, Jarrow

Touching your nose with your tongue is known as Gorlin’s Sign. It is associated with a genetic disorder but not everyone that can do it has the disorder. About 10% of people without the disorder can touch their nose with their tongue and it does not appear to be due to genes you have inherited from your parents.

5. Why do we get goosebumps? – Billingham South Community School

We often get goosebumps when we’re cold, but they don’t do much to help us warm up, so why do we get them? Before we evolved to be modern humans, our ancestors were much hairier, we they got cold, getting goosebumps would cause their hairs to stand on end. As they had much more hair than us, they were able to trap a layer of air in the hair by doing this, providing them with extra insulation to keep them warm.

Although goosebumps are no longer helpful to us, we haven’t lost the trait through evolution because it doesn’t harm us. Therefore if a person was born with a mutation in their genes meaning they didn’t get goosebumps, they wouldn’t be at an advantage because of it so the non-goosebump genes wouldn’t necessarily be passed on more than the goosebump genes.


If you have any STEM related questions that you would like us to answer, just leave a comment in the box below!

#TryThisTuesday: Cup Drop

For the week’s science demonstration, you will need a metal mug or screw, a pencil and string.


  1. Tie one end of your string onto the handle of the mug and the other to your bolt.
  2. Hold onto the screw and pick up your pencil with your other hand.
  3. Lift up the string with the pencil and hold it about half way along the string, on the same level as the screw, allowing the cup hang down.

What do you think will happen from this position if you let go off the screw?

You may think that the cup will simply fall to the floor due to the pull of gravity and the string will pull the screw along, leaving you holding a pencil mid-air.

In reality, nothing (hopefully) hits the floor. You are right in thinking, gravity wants to pull the cup down, but it also wants to pull the screw down too. As the cup begins to drop it pulls the string, pulling the screw in towards the pencil, as the screw is being pulled from two directions it ends up swinging towards them. As it has a bit of weight behind it, it builds up enough momentum to go around the pencil a few times, wrapping the string around it.

So now the string is wrapped around the pencil and the cup still hasn’t dropped. If you try to pull the screw now, you’ll see why. It’s difficult to move the string. This is due to the force of friction. Friction is a force that occurs between two objects, it is the resistance that occurs when they move over each other. As the string is wrapped around the pencil a few times, there is a larger area of string touching the pencil, so a greater force of friction. This keeps the string in place to stop it sliding off, allowing the cup to hit the floor.

Try this out with your family and friends, see if you they can guess it correctly!