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Check Your Understanding Suppose the resistive force of the air on a skydiver can be approximated by . If the terminal velocity of a 100-kg skydiver is 60 m/s, what is the value of b?
0.27 kg/m
| Magnitude of static friction | |
| Magnitude of kinetic friction | |
| Centripetal force | |
| Ideal angle of a banked curve | |
| Drag force | |
| Stokes’ law |
Athletes such as swimmers and bicyclists wear body suits in competition. Formulate a list of pros and cons of such suits.
The pros of wearing body suits include: (1) the body suit reduces the drag force on the swimmer and the athlete can move more easily; (2) the tightness of the suit reduces the surface area of the athlete, and even though this is a small amount, it can make a difference in performance time. The cons of wearing body suits are: (1) The tightness of the suits can induce cramping and breathing problems. (2) Heat will be retained and thus the athlete could overheat during a long period of use.
Two expressions were used for the drag force experienced by a moving object in a liquid. One depended upon the speed, while the other was proportional to the square of the speed. In which types of motion would each of these expressions be more applicable than the other one?
As cars travel, oil and gasoline leaks onto the road surface. If a light rain falls, what does this do to the control of the car? Does a heavy rain make any difference?
The oil is less dense than the water and so rises to the top when a light rain falls and collects on the road. This creates a dangerous situation in which friction is greatly lowered, and so a car can lose control. In a heavy rain, the oil is dispersed and does not affect the motion of cars as much.
Why can a squirrel jump from a tree branch to the ground and run away undamaged, while a human could break a bone in such a fall?
The terminal velocity of a person falling in air depends upon the weight and the area of the person facing the fluid. Find the terminal velocity (in meters per second and kilometers per hour) of an 80.0-kg skydiver falling in a pike (headfirst) position with a surface area of .
115 m/s or 414 km/h
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