Name __________________________________ Date _________________
Partners _________________________________________________________________
Apparent Weight in Elevators (and Newton's Laws of Motion): Lab #6
By M. Derengowski-Stein, M.L. West
Objective: to experience and understand the various accelerations in an elevator
Equipment: a working elevator, a scales or spring, a mass such as a person.
Background: a) Define weight:
A person of mass 60 kg has a weight of ____________
A box of weight 110 Newtons has a mass of ____________
On the moon (g = 1.62 m/s2 ) this box would have a weight of _________________________
and a mass of __________
b) Draw a free-body diagram of a 60 kg person standing on the floor.
Label each of the forces acting on her.
Label the object causing each force.
Label the magnitude of each of these forces.
c) Draw a free-body diagram of a 60 kg person standing on a bathroom scale on the floor.
Label each of the forces acting on her.
Label the object causing each force.
Label the magnitude of each of these forces.
d) Draw a free-body diagram of the bathroom scale (1 kg) on the floor with the 60 kg person standing on
the scale.
Label each of the forces acting on it.
Label the object causing each force.
Label the magnitude of each of these forces.
Which force produces the reading on the scale?
e) Draw a free-body diagram of an elevator of mass 200 kg suspended from a cable
Label each of the forces acting on it.
Label the object causing each force.
Label the magnitude of each of these forces.
2
f) If the elevator is traveling upwards at a velocity of 2 m/s, what are the magnitudes of the forces on it?
g) If the elevator accelerates upwards, then will the forces acting on it add up to zero? ______
Explain:
Which force will change?
Which force remains the same?
If the upwards acceleration is 3 m/s2, then what is the magnitude of each force?
h) If the elevator accelerates downward at 3 m/s2, then what is the magnitude of each force?
i) Now a 60 kg woman enters the elevator. When the elevator is stationary what are the forces and their
magnitudes acting on her?
j) If the elevator is moving downward with a constant velocity of 2.5 m/s, then what is the magnitude of
each force acting on her?
k) If she is standing on a scale in the elevator moving downward with a constant velocity of 2.5 m/s, then
what is the magnitude of each force acting on the scale?
l) If she is standing on a scale in the elevator then what is the magnitude of each force acting on the scale
if the upwards acceleration is 3 m/s2?
m) If she is standing on a scale in the elevator then what is the magnitude of each force acting on the
scale if the acceleration is 3 m/s2 downwards?
3
Procedure:
Each team will have one bathroom scale and one spring scale with a mass. Do three trials of each
situation and average the results. The acceleration will take place quickly, so try to read the scale
quickly.
Situation
Scale
Scale
Scale
Spring
reading, reading, reading, scale,
trial 1
trial 2
trial 3
trial 1
Spring
scale,
trial 2
Spring
scale,
trial 3
Scale, Spring
ave
scale,
ave
Stationary
Scale/ Spring
statio scale/
nary
station
ary
1.0
1.0
Moving up,
increasing
speed
Moving up,
constant speed
Moving up,
decreasing
speed
Moving down,
increasing
speed
Moving down,
constant speed
Moving down,
decreasing
speed
If a person on the bathroom scales suddenly jumps upward off the scales, what happens to the reading on
the scales? (Please don't break the scales. Jump to land on the floor.)
Conclusions: Summarize your observations in 100 words or less.
How can you use Newton's laws of motion to explain your results?
Further Research: Make several suggestions as to further use for this equipment.
a