Terminal speed
Objects moving in water or air
When objects move faster in air (or water), air resistance or A friction force that opposes the motion of an object in air or water. Usually this is air resistance. This resistance depends on the speed of the object and its surface area. forces increase. As the drag forces increase, the resultant force is reduced. When the drag forces become the same as the weight or the thrust, then the forces become balanced (equal and opposite). There is now no resultant force and the object stops accelerating, but continues to move at constant speed. This constant speed is called terminal speed or The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces..
Question
As a skydiver moves through the air, what stays constant, weight or drag?
Weight. The drag changes with the speed of the skydiver.
Question
Look at pictures A, B, and C. Work out the resultant force of the skydiver, and the acceleration if the skydiver has a mass of 60 kg.
Picture A
The resultant force is 600 N. The acceleration will be
a = F ÷ m
= 600 N ÷ 60 kg
= 10 m/s2
This is called the acceleration due to gravity.
Picture B
The resultant force is 600 – 100 = 500 N.
The acceleration will be
a = F ÷ m
= 500 N ÷ 60 kg
= 8.3 m/s2
Notice that the acceleration is getting less as the drag starts to increase.
Picture C
The resultant force is 600 – 600 = 0 N.
The acceleration will be zero, as there is no resultant force.
