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Typical values of drag coefficient C
Object C
Airfoil 0.05
Toyota Camry 0.28
Ford Focus 0.32
Honda Civic 0.36
Ferrari Testarossa 0.37
Dodge Ram Pickup 0.43
Sphere 0.45
Hummer H2 SUV 0.64
Skydiver (feet first) 0.70
Bicycle 0.90
Skydiver (horizontal) 1.0
Circular flat plate 1.12

Substantial research is under way in the sporting world to minimize drag. The dimples on golf balls are being redesigned, as are the clothes that athletes wear. Bicycle racers and some swimmers and runners wear full bodysuits. Australian Cathy Freeman wore a full body suit in the 2000 Sydney Olympics and won a gold medal in the 400-m race. Many swimmers in the 2008 Beijing Olympics wore (Speedo) body suits; it might have made a difference in breaking many world records ( [link] ). Most elite swimmers (and cyclists) shave their body hair. Such innovations can have the effect of slicing away milliseconds in a race, sometimes making the difference between a gold and a silver medal. One consequence is that careful and precise guidelines must be continuously developed to maintain the integrity of the sport.

A photograph of three swimmers wearing body suits.
Body suits, such as this LZR Racer Suit, have been credited with aiding in many world records after their release in 2008. Smoother “skin” and more compression forces on a swimmer’s body provide at least 10 % less drag. (credit: NASA/Kathy Barnstorff)

Terminal velocity

Some interesting situations connected to Newton’s second law occur when considering the effects of drag forces upon a moving object. For instance, consider a skydiver falling through air under the influence of gravity. The two forces acting on him are the force of gravity and the drag force (ignoring the small buoyant force). The downward force of gravity remains constant regardless of the velocity at which the person is moving. However, as the person’s velocity increases, the magnitude of the drag force increases until the magnitude of the drag force is equal to the gravitational force, thus producing a net force of zero. A zero net force means that there is no acceleration, as shown by Newton’s second law. At this point, the person’s velocity remains constant and we say that the person has reached his terminal velocity     ( v T ) . Since F D is proportional to the speed squared, a heavier skydiver must go faster for F D to equal his weight. Let’s see how this works out more quantitatively.

At the terminal velocity,

F net = m g F D = m a = 0 .


m g = F D .

Using the equation for drag force, we have

m g = 1 2 C ρ A v T 2 .

Solving for the velocity, we obtain

v T = 2 m g ρ C A .

Assume the density of air is ρ = 1.21 kg/m 3 . A 75-kg skydiver descending head first has a cross-sectional area of approximately A = 0.18 m 2 and a drag coefficient of approximately C = 0.70 . We find that

v T = 2 ( 75 kg ) ( 9.80 m/s 2 ) ( 1.21 kg/m 3 ) ( 0.70 ) ( 0.18 m 2 ) = 98 m/s = 350 km/h .

This means a skydiver with a mass of 75 kg achieves a terminal velocity of about 350 km/h while traveling in a pike (head first) position, minimizing the area and his drag. In a spread-eagle position, that terminal velocity may decrease to about 200 km/h as the area increases. This terminal velocity becomes much smaller after the parachute opens.

Questions & Answers

what is velocity
Austine Reply
speed per unit time is called velocity. it is a vector quantity
velocity is distances overall time taking,it is a vector quantity, the units is metre per second.
what is the difference between resultant force and net force
Ogali Reply
net force is when you add forces numerically I.e. the total sum of all positive and negative or balanced and unbalanced forces. resultant force is a single vector which is the combination or addition of all x and y axes vector component forces in a system.
Damping is provided by tuning the turbulence levels in the moving water using baffles.How it happens? Give me a labelled diagram of it.
Shaina Reply
A 10kg ball travelling at 4meter per second collides elastically in a head-on collision with a 2kg ball.What are (a)the velocities and (b)the total momentum of the balls after collision?
Law Reply
a)v1 8/3s&v2 20/3s. b)in elastic collision total momentum is conserved.
The displacement of the air molecules in sound wave is modeled with the wave function s(x,t)=5.00nmcos(91.54m−1x−3.14×104s−1t)s(x,t)=5.00nmcos(91.54m−1x−3.14×104s−1t) . (a) What is the wave speed of the sound wave? (b) What is the maximum speed of the air molecules as they oscillate in simple harmon
Shaina Reply
practical 1st year physics
Nsc Reply
Whats the formular for newton law of motion
Ahmad Reply
F=m×a Where F=force M=mass of a body of an object a=acceleration due to gravity
what is speed
Hassan Reply
distance travelled per unit of time is speed.
distance travelled in a particular direction it is.
Speed is define as the distance move per unit time. Mathematically is given as Speed = distance/time Speed = s/t
speed is a vector quantity. It is defined distance per unit time.It's unit in c.g.s cm/s and in S.I. m/s.It’s dimension is LT^-1
formula for velocity
Amraketa Reply
v=ms^-1 velocity=distance time
(p-a/v)(v-b)=nrt what is the dimension of a
velocity= displacement time
Velocity = speed/time
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Shaina Reply
If the block is displaced to a position y , the net force becomes Fnet=k(y−y0)−mg=0Fnet=k(y−y0)−mg=0 . But we found that at the equilibrium position, mg=kΔy=ky0−ky1mg=kΔy=ky0−ky1 . Substituting for the weight in the equation yields. Show me an equation of graph.
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samastipur Bihar
simple harmonic motion defination
Maharam Reply
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Sayed Reply
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bonokuhle Reply
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can u tell me the expression for radial acceleeation
Shikha Reply
Is equal to the square of the velocity divided by the radius of circular path of the object
how to find maximum acceleration and velocity of simple harmonic motion?
how to find maximum acceleration and velocity of simple harmonic motion and where it occurres?
you can use either motion equations or kinetic equation and potential equation .
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A Radial Acceleration is defined as the upward movement of an object.
A body of 2.0kg mass makes an elastic collision with another at rest and continues to more in the original direction but with 1/4 of its ori is the mass of the struck body?
bright Reply
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Practice Key Terms 2

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