How Surface Area Of Vanes Effect The
Rate At Which A Weight Drops
Aim – To see if the surface area of a wind vane affects the rate at which a weight drops from it.
Hypothesis – I predict that by increasing the surface area of the vanes on the wind vane, I will increase the air resistance therefore slowing the rate at which the weight will drop.
Primary Work – If a piece of paper and a marble are in free fall, they will fall at the same speed, so they should hit the ground at the same time. If you test this by just dropping a marble and a piece of paper you will find it is not true. This is because the objects are not in free fall. To be in free fall, gravity has to be the only force acting on the objects. When you just drop something, there is also air resistance. Air resistance is a type of fluid friction. Because friction acts in the opposite direction of the object’s motion, air resistance of an object falling downward is an upward force. This is because a falling object is coming down, so the opposite direction is up. If air resistance were equal for every object, objects would still fall at the same rate. Since we know they do not fall at the same rate, we know air resistance is different for different objects. The amount of air resistance acting on an object depends on the object’s surface area. If an object has a small surface area, it will have little air resistance. Because the piece of paper has a larger surface area than the marble, the marble will have less air resistance than the piece of paper and the paper will fall slower. This is what I expect to happen with a wind vane. As the wind vane turns, air resistance will act on each of the separate vanes. By increasing the surface area of the vanes, I will increase the air resistance therefore making the rate at which the weight drops slower, because there is more opposing force.
