Sky High
Playing with the Centre of Gravity toy that they built makes Hanuman more curious. He directs his questions at Nala’s brother Nila.
Hanuman: Are there any other forces that our body uses to stay stable?
Nila: Oh yes. There are nine forces acting on our body at all times.
Nala: Like the planets that revolve around the sun? There are forces that make them orbit the sun and keep them from floating away.
Nila: Not exactly, but these planets are also affected by various forces. When an object has mass (volume of matter) and when it moves, all these forces comes into play.
Hanuman: Don’t all planets have mass? In fact, everything that is visible to our eye has mass. And everything is in motion.
Nila: Not only the things we can see, but even invisible matter like air have mass.
Hanuman: Oh! So what are the forces acting on us?
Nila: You know gravity. It is the force that pulls us towards the centre of the Earth irrespective of whether we are in contact with the ground or not.
Nala: So, it’s a non-contact force. But how come we are not visibly moving towards the centre of the Earth then?
Nila: That is because there is another called normal force that counters gravity. It is what surfaces exert to prevent solid objects from passing through each other.
Hanuman: So, this one will be contact force?
Nila: That’s right. It is what keeps a surface solid.
Hanuman: What’s the next?
Nila: Applied force. Anything you do consciously like taking, throwing, jumping, and so on falls under an applied force. It just means that you are applying a force to do some work.
Hanuman: Next…
Nila: This one’s related to you: air resistance. On a windy day, try walking or running, especially with your hands open. You may feel the air “pushing” you. Your hair flying in the wind is also an example.
Hanuman (beaming): My dad must be proud to have a force of his own!
Nila: Next is a force you are both familiar with. Remember the reason for Sampati’s burnt wings? (Refer episode)
Nala: Oh yes! Friction! It is the force that resists motion when the surface of one object comes in contact with the surface of another.
Hanuman: That’s five so far.
Nila: The sixth is elastic or spring force; the ability of any mass to try and regain its original shape when the forces are removed pretty much like a spring! Or a rubber band.
Nila: Next is tension force; opposite to elastic force that is transmitted through a cable, rope, wire or string when it is pulled tight by forces acting from opposite ends. Like the string of a bow. Tension can only pull on an object. Like how you cannot push using a rope; it will go limp. But you can pull an object using one.
Hanuman: Only two more left now...
Nila: Both are non-contact forces. One is magnetic force. Notice how the compass’s needle always points to the North no matter how you move. That’s because the Earth is a giant magnet.
Hanuman: Really?!
Nila: Yes. Just like a magnet, it has a north and south magnetic pole and a magnetic field that protects the living organisms on the planet from the sun’s harmful radiation.
Hanuman: This is news to me!
Nila: And the final non-contact one is electric force. Do you know what it is?
Nala: It is the attractive or repulsive force between two charged bodies.
Nila: Right. The power that lights up a bulb; the way hair stands up when rubbed with a balloon; and even the mild shock we experience when touching a doorknob are all examples of electric force at play.
Types of forces
Hanuman: Woah! So now that’s a total of six contact and three non-contact forces.
Nila: If you are interested, I can tell you more about each of these forces and how they play a major role in our universe.
Hanuman: Yes, please! But first I need a snack. I am quite famished.
Nala: Yes. We need a snack break. The solar system can’t handle Hanuman’s hunger one more time.
The three of them burst into laughter and proceed into the cafeteria inside Nila’s workshop, which had more surprises in store.
The writer is the founder and CEO of Vaayusastra Aerospace, an IIT-Madras incubated ed-tech startup that offers Air Science workshops for children between five and 14 years.
