PASCO ME-9426A AMUSEMENT PARK PHYSICS - Manual (Page 9)

012-03776E Amusement Park Physics
5
Multiply g by the tangent of the angle to the center of the
BB.
To use the horizontal accelerometer to measure horizon-
tal centripetal accelerations, hold it perpendicular to the
direction in which you are headed and as level as possible.
For example, on the rotor ride at an amusement park,
where you are in a rotating cylinder feeling mashed to
the wall, hold the accelerometer with the short side
pressed to the wall. It will be level with the floor and,
since you are traveling sideways, perpendicular to the
direction of travel.
Before the motion begins, the BBs sit in the bottom of
the tube. When the ride begins to rotate, a centripetal
force is needed to make them go in a circle. The BBs will
ride up the side nearest the wall, as if forced outward. In
fact, the tube will be exerting a horizontal force on them
directed in toward the center of the ride. They will ride
up until the angle is large enough to give the necessary
horizontal acceleration. In circular motion
where v is the linear speed along the circumference and
r is the radius of the circle. As the ride picks up speed,
the BBs will travel farther up the curve.
Using the Horizontal Accelerometer as a
Sextant
The horizontal accelerometer can be used to measure the
heights of objects that are too high to measure directly,
such as measuring the height from the ground to the top
a
v
2
r
----- =
of King Kong's head, in Figure 3. You can measure these
distances with reasonable accuracy using just the accel-
erometer, a piece of string that is marked out in meters,
and a little trigonometry. The procedure is as follows:
1. Measure the distance S with a piece of string marked
out in meters.
S is the horizontal distance between your point of
observation and a point directly below the object of
interest.
2. Sight through the straw to the top of King Kong's
head, and measure the angle
θ on the accelerometer.
θ is the angle that the center BB aligns with on the
horizontal accelerometer. It is also the angle between
your horizontal line of sight and your line of sight to the
top of King Kong's head.
3. Measure h
0
, the vertical distance between the base
of your height measurement and your observation point.
As long as the ground is level between you and the
building on which King Kong is standing, h
0
is just the
distance from the ground to your eyes.
4. Then:
H = h
0
+ h
1
= h
0
+ S tan θ.
mg
ma
-mg
θ
θ
Direction of
Acceleration
Force applied
by tubing
Figure 2: Diagram of the Horizontal Accelerometer
S
H
h
1
h
0
θ
θ
Figure 3: Measuring Heights with the Horizontal
Accelerometer