Name_____________________ Pd. _____
PHYSICS LAB: DETERMINATION OF THE ACCELERATION OF AN ELEVATOR.
INTRODUCTION:
In order for an object to accelerate, there must be a net force acting on it. We know that the direction of the
acceleration will be in the same direction as the direction of the net force. The equation for Newton’s 2nd law is
F = ma or a = F/m
Today we will be looking at the acceleration of an elevator when it starts and stops. Since acceleration and
force are vector quantities, we must distinguish between up and down. Our sign convention will be positive for
up and negative for down. Therefore the force of gravity, Fg is negative and the force exerted by the elevator,
FN is positive. FN is your “apparent weight” measured by the bathroom scale you will be standing on while the
elevator accelerates. Since there are only 2 forces acting on you in the elevator, the net force, F is just the
vector sum of the 2 forces.
F = FN + Fg
FN (+)
If acceleration is upwards, F = (+)
If acceleration is downwards, F = (-)
Fg (-)
PREDICTION: Have you ever ridden in an elevator? If not, you will today! Think about how you feel when you
are in an elevator, does it feel like your weight changes? Fill out the following chart and predict whether or not
you weight will increase, decrease, or stay the same.
Going up
Going down
Starting
In the middle
Stopping
OBJECTIVE : Determine the acceleration of an elevator using a bathroom scale.
MATERIALS: Bathroom scale, elevator
PROCEDURE:
1. Determine your actual weight by standing on a bathroom scale. If the scale is graduated in pounds,
convert pounds to kilograms by using the conversion 2.2 LB = 1 kg. Then calculate the weight in
Newtons by multiplying your mass in kg by 9.8 N/kg. What equation is this that you are using??
Weight: __________lbs __________kg ____________N
2. While standing on the scale in an elevator, press the up button. Have your partner ready to read the
maximum weight attained just as the elevator accelerates. Convert to Newtons. Record the data in the
up column.
3. When the elevator approaches the next stop, have your partner read the scale just as the elevator
decelerates to a stop. Determine the minimum weight attained while decelerating. Convert to Newtons.
Record the data in the up/stop column.
4. While standing on the scale in an elevator, press the down button. Have your partner ready to read the
minimum weight attained just as the elevator accelerates.
Name_____________________ Pd. _____
5. When the elevator approaches the next stop, have your partner read the scale just as the elevator
decelerates to a stop. Determine the maximum weight attained while decelerating. Convert to Newtons.
Record the data in the down/stop column.
*** Be sure to express forces and weights with the appropriate signs, + for up and - for down***
DATA AND CALCULATIONS:
UP/START UP/MIDDLE UP/STOP
DOWN/START DOWN/MIDDLE DOWN/STOP
1) Apparent
Weight (LB)
2) Mass (kg)
3) Apparent
Weight (N)
4) ΣF(N)
5) Acceleration
= ΣF/m
CONCLUSIONS:
1. How does the acceleration you experience in an elevator compare to that you might experience in a car
that accelerates from 0 to 60 miles per hour in 7 seconds? Remember to express accelerations in m/s2.
2. Identify those places in the ride when the scale reads a “heavier” value. In which direction is the
acceleration?
3. Identify those places in the ride when the scale reads a “lighter” value. In which direction is the
acceleration?
4. Identify those places in the ride when the scale reads the true weight of the person. Are the forces
balanced or unbalanced?
5. What would the scale read if you were accelerating downward at 9.8 m/s2? (FBD!!!!)
6. What would the scale read if you were acceleration upward at 9.8 m/s2? (FBD!!!!)