The Leaning Tower of Pisa - Galileo's Experiment

I went on holiday to Italy not long ago and whilst I was there, I visited the Leaning Tower of Pisa. This is the place of Galileo’s experiment where he dropped two cannonballs of different masses to see  whether they would hit the ground at the same time. They did. 

Many people would argue that they wouldn’t (if they didn’t know the outcome of the experiment already). This is understandable as common sense tells you that heavier objects have a larger force of attraction and will therefore accelerate towards the Earth faster than lighter ones. However, acceleration is not just derived from force, it also depends on mass (a = F/m, acceleration = force / mass, Newton’s Second Law of Motion). 

Let’s substitute some figures into a = F/m. Take a 1kg chinchilla and 100kg panda. If we were to only think about the force acting on these animals (ignoring air resistance), the panda would hit the ground first. This is because 100kg, the panda’s mass, results in 1000N of downward force (due to the Earth’s gravitational field strength of around 10N/kg). The chinchilla’s downward force would only be 10N. Now let’s put the effect of the animals’ masses into a = F/m.

acceleration = (1000 N / 100 kg) = 10 m/s/s

acceleration = (10 N / 1 kg) = 10 m/s/s

The acceleration is the same regardless of the force. The panda's mass gives it more inertia (this is an object's resistance to changes in its current state of motion), this means it is more difficult to get the panda moving compared to the chinchilla. The panda's mass has an inverse effect on its acceleration and therefore causes the two animals to accelerate at the same rate.