Hello steemians ! Guys physics is really interesting guys . This is one of topic that I think can change your perceptional on physics . I am sure that you will love this one .
Today I want to share you about an activities that related to Physics . That's skydiving , in skydiving there there an interaction involved ,between the gravity and the air resistance . The skydiver will start accelerating downwards when they jump the plain this happen until the skydiver reaches terminal speed.
This is speed where drag the skydiver from the air resistance and it's will stabilize the force the gravititional force that pull the skydiver down. Below is the figure shows how this happen .
Where:
Gravity acceleration ,g = 9.8m/s²,
m = Skydiver mass
D = Upward drag force
W = Gravity force
v = Speed
vt = constant (terminal) speed the skydiver reaches when D = W
When D< W his speed will increasing , The Newton's Second Law said that, ΣF = ma, and ΣF = W − D, acceleration, a is positive and v will increases.
The general equation for drag force on a body is:
Where:
Drag coefficient , C can vary along with the speed of the body . Usually the typical values range from 0.4 to 1.0 for different fluids, such air and water .
ρ is the fluid density through a moving body for this cases, the air is the fluid .
v is the body speed that relative to the fluid(air)
A = projected cross-sectional area of the body and it isperpendicular to the flow direction ( perpendicular to v). This can be illustrated as
The force of gravity pulling the skydiver down is:
W = mg
When, D = W terminal speed is reach so we have
Solving for terminal speed vt we have ,
Area A small cross sectional area is the higher terminal speed . The skydiver need to decrease his A value if he want to catch up to his fellow skydiver, he can do that by decreasing his A value. Your head must be facind down to do that .
Another important factor is mass of an object . We can see when the feather will fall much more slowly than a solid object such as a stone, this because the drag force relative to body weight (mg) is much higher for a feather.
In the spread eagle position (shown in the picture) they can reach 120 mph . But he also can reach speeds up to 200 mph if he orients his body with head pointing down it can decreasing his A.
Variety of acrobatic maneuvers such as spinning, moving forward, moving backward can they perform just by changing the shape of his body to "catch" the wind a certain way while they are in free fall.
Drag force will essentially changing the direction of the drag force acting on his body by doing this , same like an airplane wings, it can be oriented to produce a desired motion for the plane.
Last but not least , the final drag force, the skydiver should be practised or experience is from releasing his parachute, slows his descent to make sure he land safely.
Interesting right , don't read only you also need watch the video below , to feel the wind guys . Hahaha thanks for reading !
So , now we know that whatever we do , activities ,works and so on . It's related to #physics .
