Surprising as it might seem, an object’s mass has no impact on how fast it falls. Instead, its speed is determined by a property of gravity called gravitational acceleration (or g for short), which is 9.81 metres per square second at the surface of our planet. This means that in one second, any object’s downward speed will increase by 9.81 metres (32.2 feet) per second because of gravity, regardless of mass. Having said that, if you imagine dropping a feather and a hammer at the same time, you don’t need to be a physicist to guess that the hammer will fall faster (mind your toes!). Gravity accelerates both objects at the same rate, but another factor comes into play: air resistance. The feather is slowed down more by the air and floats down gently, while the hammer crashes straight to the ground.
Apollo 15 astronauts tried out this exact experiment on the Moon where there is no air, and consequently no air resistance – both hammer and feather landed at the same time. Back here on Earth, if you dropped two objects with exactly the same shape and volume but different mass, they would also fall at the same speed.
Answered by Alexandra Cheung.