# Air Resistance & Terminal Velocity (1 Viewer)

#### _Anonymous

##### Member
So we all know that if we dropped a feather and a bowling ball from the same height, the bowling ball would land much quicker since the feather has a larger surface area and the air molecules make it "float" more (that's what I learnt from my Science teacher, so correct me if that's wrong). Now hypothetically speaking; if we had a 5kg bowling ball and another bowling ball which has a mass of 500g, would the 5kg ball reach the ground quicker this time or would they both land at the same time due to their similar surface area?

Also, I don't understand why terminal velocity is a thing. People say that since an object (falling from a plane for example) has gravity pulling it down to the Earth, it will eventually have a zero net force due to the air resistance force equalling the force of gravity. How does the air resistance force equal to the one of gravity? Could someone please explain? Also, people say that a lighter object will reach terminal velocity much quicker than a heavier one, why?

#### jazz519

##### Moderator
Moderator
So we all know that if we dropped a feather and a bowling ball from the same height, the bowling ball would land much quicker since the feather has a larger surface area and the air molecules make it "float" more (that's what I learnt from my Science teacher, so correct me if that's wrong). Now hypothetically speaking; if we had a 5kg bowling ball and another bowling ball which has a mass of 500g, would the 5kg ball reach the ground quicker this time or would they both land at the same time due to their similar surface area?
Yes they will both land at the same time (since the air resistance on both will be similar)

Also, I don't understand why terminal velocity is a thing. People say that since an object (falling from a plane for example) has gravity pulling it down to the Earth, it will eventually have a zero net force due to the air resistance force equalling the force of gravity. How does the air resistance force equal to the one of gravity? Could someone please explain?
the air resistance force is dependent on how fast the object is moving. So essentially the faster you move, the greater the air resistance, because more air molecules are striking the leading surface of the object per second as its speed increases. But at a certain point that force becomes too big and it can no longer accelerate and thus the forces balance and terminal velocity is reached.

Also, people say that a lighter object will reach terminal velocity much quicker than a heavier one, why?
Heavy objects will have a higher terminal velocity than light objects, because it takes a greater air resistance force to equal the weight of a heavier object, and remember a larger air resistance force needs more speed.

#### red152

##### Member
jazz wouldn't the 5kg one fall faster? Isn't the force exerted on an object increased with its mass?

#### jazz519

##### Moderator
Moderator
jazz wouldn't the 5kg one fall faster? Isn't the force exerted on an object increased with its mass?
Yes the force increases but the acceleration is the same (greater force for the heavier still results in a 9.8m/s^2 acceleration assuming there is no air resistance or the effects are similar i.e. same type of ball surface, shape and size and the same will happen for a 500g ball it will experience a smaller force but the same acceleration overall)

#### red152

##### Member
Yes the force increases but the acceleration is the same (greater force for the heavier still results in a 9.8m/s^2 acceleration assuming there is no air resistance or the effects are similar i.e. same type of ball surface, shape and size and the same will happen for a 500g ball it will experience a smaller force but the same acceleration overall)
oh im dumb

#### jazz519

##### Moderator
Moderator
oh im dumb
Nah its fine, its a common misconception. This guy has really good videos on these types of things (not always related to HSC but still enjoyable to watch):

#### _Anonymous

##### Member
Yes they will both land at the same time (since the air resistance on both will be similar)

the air resistance force is dependent on how fast the object is moving. So essentially the faster you move, the greater the air resistance, because more air molecules are striking the leading surface of the object per second as its speed increases. But at a certain point that force becomes too big and it can no longer accelerate and thus the forces balance and terminal velocity is reached.

Heavy objects will have a higher terminal velocity than light objects, because it takes a greater air resistance force to equal the weight of a heavier object, and remember a larger air resistance force needs more speed.
Ahh I got it now, thank you!