Angry Birds is an iPhone timewasting sensation that has been sweeping the nation, simple to get into and fun to play. You pull back the bird in the catapult and aim it at the pigs that make up your target. Simple! How can physics help me? (I hear you cry)
Well, the path that the birds take after they are released from the catapult is the same (only slower in speed, so you can fully enjoy the fruits of your labour) as you would expect from most things that you throw into the air. It’s the same as the way a football flies from a goal kick, the way a tennis ball arcs over the net, and even the same as that stinky sock your brother threw at your face yesterday.
These are all called projectiles, which is often a word only associated with bombs and weapons (ok, the sock might be a weapon too), but in Physics it’s used to describe anything that moves through the air when the only force working on it is gravity. This doesn’t mean that you can’t give the projective a head start by chucking it as hard as you can, only once it leaves your hand it hasn’t got any way of changing its own direction. An example of something that does have its own methods of moving might be a remote controlled plane, or a bird (but thankfully the angry birds don’t seem to know how to move their wings, making them fall firmly in the projectiles category).
Also, when we talk about projectiles we mean things that look quite a lot like the angry birds, roundish items that haven’t got a lot of wind resistance, that can’t float in the air, so that means that feathers, paper aeroplanes and umbrellas are out too.
So now we know what we mean by projectiles, we can see what they have in common. We know that they are all given a starting push, just like our angry birds who are catapulted. This push is often known as thrust, and we can measure both the speed of this as well as the angle (measured from the floor).
Once the bird (or projectile) has left our control there is nothing to do but wait and see what happens, we can’t change anything, the only force working on the projective is gravity, which works to bring everything back down to earth.
Looking more closely at what effects the thrust and the angle have on the bird, we can see first that by changing the thrust, which relates directly to the amount you pull back the catapult, the bird unsurprisingly goes further. So more thrust equals more distance, when we keep the angle the same.
But it all get a little more complicated when we start to change to angle, and keep the speed the same. As the angle between the floor and the catapult increases, at first we get the bird to go further. But increase it more and our projectile starts to go up higher into the air and then land nearer us.
In fact, if we look at the numbers more closely we can work out the perfect angle for launching our birds the furthest that we possibly can, making that hard-to-reach last section of the target accessible. Next time I will delve into the equations slightly more, but for now, why not waste some time on Angry Birds and whilst you’re at it, try and see what happens when you change the speed and angles!