Download Physics trivia

Physics trivia
Coaster dynamics
1. The forces exerted on riders of roller coasters are usually expressed in units of
G's. If a person weighs 150 lbf, what would the force be in lbf at the top of a loop
if it is equal to -1.5 G's?
G force is defined as the net force on an object divided by the weight of that
object. Thus, if the net force on the person is -1.5 G's, it is equal to (-1.5)(150 lbf)
= -225 lbf. The negative sign indicates that the force is directed downward.
2. The force exerted on a roller coaster rider traveling through a loop is called
centripetal force. What is the difference between the centripetal force and
centrifugal force?
As stated in Newton's Third Law of Motion, whenever one object exerts a force
on a second object, the second object exerts an equal and opposite force on the
first. In the case of a roller coaster rider moving through loop, the force that the
car seat exerts on the rider is called the centripetal force. The equal and opposite
force that the rider exerts on the car seat is called the centrifugal force.
3. In a real roller coaster, the shape of vertical loops are never circles of constant
radius. Why?
The centripetal force in a loop is proportional to the speed. When a roller coaster
car enters a loop at the bottom at high speed, the velocity decreases as it nears the
top. Thus, the centripetal force at the top is less than at the bottom. It turns out
that for a large loop, the difference in speed is so great that the combined affect of
gravity and the centripetal force at the bottom will be dangerously high (risking
injury) in order for there to be enough force pushing the rider upward at the top
(so that he won't fall out of his seat).
4. The geometric shape used for loops in real roller coasters has a special name (it is
not a circle or ellipse). What is it called?
A klothoid (or sometimes spelled clothoid). A klothoid has a continuously varying
radius of curvature that is large at the bottom and small at the top. To learn why
this shape is preferable to a circle, see the Coaster Dynamics Physics Primer and
Coaster Lab Lesson #8.
5. If a roller coaster car were to roll over the top of a hill and then drop downward as
if it were in free fall, what geometric shape would the path take?
A parabola.
6. For a traditional, once-around loop roller coaster, with a single lift hill, where
does the energy come from that powers the cars around the track? Where does the
energy go?
All the energy comes from the work done to pull the train of cars up the lift hill.
This is stored as potential energy. That energy is then converted into motion
(kinetic energy) and is eventually consumed by the non-conservative forces acting
on the cars -- mostly friction from the wheels, and air resistance.
7. Roller coaster builders often brag about having the highest and steepest hills. If
roller coaster A has a 300 ft high hill with a descent angle of 80°, and roller
coaster B has a 310 ft high hill with an angle of 70°, which roller coaster will
have the faster speed at the bottom of the hill?
Roller coaster B. If non-conservative forces (such as friction and air resistance)
are neglected, the change in speed when going down a hill depends only on the
net change in height. However, a steeper descent angle will produce a higher
acceleration (if the steepness does not exceed the free fall trajectory). Faster
acceleration has an exhilarating physiological affect on riders... so, some may feel
that roller coaster A has a more thrilling ride, despite its lower peak speed.
8. If measured from two fixed points on the track, one shortly before and one shortly
after the top of a hill, when a train of roller coaster cars travels over the hill,
which car will have the fastest average and maximum speeds -- the first or last car
in the train?
This is a trick question. Actually, the average and maximum speeds for the first
and last cars are exactly the same (assuming we neglect the affect of nonconservative forces, such as friction and air resistance). However, there is a
difference in the motion between the first and last cars, which can make one or the
other likely to provide a more thrilling ride. See Chapter #12 of the Coaster
Dynamics Physics Primer for a discussion of this topic.
9. A new genre of roller coasters was introduced in the past decade featuring "linear
induction motors" that "launch" roller coaster trains at extremely high acceleration
rates (and at speeds up to 100 mph). For what purpose was linear induction motor
technology originally developed?
Linear induction motor technology was developed by NASA during conceptual
studies investigating the feasibility of alternate means of sending payloads into
earth orbit (other than the Space Shuttle). The concept originally studied was to
use a large linear induction motor to "shoot" payloads into earth orbit, destined for
a permanently orbiting space station. After initial studies and feasibility testing of
the technology, the proposal was abandoned. However, the project definitely
wasn't a loss... since it spawned a new "space-age" of thrilling roller coasters!
10. What is the name most frequently given to roller coasters throughout the history
of amusement parks?
Cyclone. One of the earliest, and most famous, roller coasters ever built was the
Coney Island Cyclone, opened in 1927 at Coney Island, New York. Through the
decades, that coaster has inspired dozens of replicas and hundreds of other roller
coasters throughout the world named Cyclone, or coasters with Cyclone as part of
its name.