An object moving through a fluid (e.g. air or water) experiences a resistive drag force from the fluid. Drag is a frictional force that opposes the motion of the object through the fluid. Drag is influenced by the shape and the speed of the object. Drag increases with speed and is proportional to the square of the speed.
When an object falls through a fluid, initially there is only the weight acting on the object and the acceleration is g
Drag also increases with cross-sectional area.
As speed increases, drag increases,
the acceleration decreases to less than g.
Eventually drag = weight
When this happens the object has reached a terminal velocity. There is no resultant force so there is no acceleration
The following apparatus can be used to investigate the motion of an object in a fluid.
A velocity time graph of the polystyrene ball is generated on the laptop by the motion sensor, data logger. The motion of the polystyrene ball is identical to the motion of the object in the fluid.
When an object falls through a fluid, initially there is only the weight acting on the object and the acceleration is g
Drag also increases with cross-sectional area.
As speed increases, drag increases,
the acceleration decreases to less than g.
Eventually drag = weight
When this happens the object has reached a terminal velocity. There is no resultant force so there is no acceleration
The following apparatus can be used to investigate the motion of an object in a fluid.
A velocity time graph of the polystyrene ball is generated on the laptop by the motion sensor, data logger. The motion of the polystyrene ball is identical to the motion of the object in the fluid.