PASCO ME-9426A AMUSEMENT PARK PHYSICS - Manual (Page 15)

012-03776E Amusement Park Physics
11
Objective
During this lab you will determine the vertical accelerations in an elevator using an accelerometer. You will also
analyze the motion of an elevator.
Discussion
The net force on the mass in the accelerometer is given by the relationship
:
F
s
- mg = F
net
= ma
net
where F
s
is the force applied by the spring to the mass, and mg is the weight due to gravity of the mass. When
the mass is at rest or moving with constant speed in an upward or downward direction, the upward pull of the
spring is equal in magnitude to the downward pull of the weight. In these cases, the net force is zero and the net
acceleration of the mass is zero. If the accelerometer is calibrated to read "1g" when it is at rest, that recognizes
the 1g effect of gravity. To get the net acceleration of zero, you subtract 1g from the reading. If the mass is
accelerating upward, it will be in a position below "1g" or at a reading greater than 1g. Again, the net acceleration
can be determined by subtracting 1g from the accelerometer reading. The reading will still be above zero (positive)
indicating an upward acceleration. If the mass is accelerating downward, it will be above the "1g" position, or a
reading of less than 1g. Subtracting 1g will yield a negative net acceleration in agreement with the downward
acceleration of the mass.
Procedure
Hold the accelerometer vertical by pressing it to the wall of the elevator. Take readings in each of the following
instances (see Table 5).
Questions
1. Are the magnitudes of the accelerations different at the beginning of the ascent than in the middle of the ascent?
Explain why this is so.
2. Are the magnitudes of the accelerations different at the middle of the ascent than at the middle of the descent?
Explain why this is so.
Table 5:
Trial 1 Trial 2 Trial 3
Standing still
Beginning ascent
Middle of ascent
Slowing ascent
Stopped
Beginning descent
Middle of descent
Slowing descent
Stopped
Experiment 3: Elevator Physics