Required Equipment :
- Motion Sensor
- PascoCart
- Track
- End Stop
- Pulley with clamp
- Hanger Mass Set
- String (about 1 m)
- 250 gr Cart Mass
Purpose
Figure 4.1
In this experiment, you will verify Newton’s Second Law, F
m a , and then acceleration due to gravity g.
Theory
According to Newton’s Second Law , F = m a , where F is the net force acting on the object of mass m , and a is the resulting acceleration of the object.
For system of a cart of mass m
1 on a horizontal track that is connected to a hanging mass m
2
(Figure 4.1) with a string over a pulley, the net force F on the entire system ( Cart and hanging mass ) is the weight of hanging mass. F = m
2 g (no friction assumed).
According to Newton’s Second Law, m
2
g = (m
1
+ m
2
) a
Procedure
1Install the feet on the track and level it.
2Install the end stop on the track near one end with the magnets facing away from the track.
3Measure the mass of the PasCart and record it in Table 4.1.
4Attach the pulley and end stops on the track as shown in Figure 4.1. Place the cart on the track.
Tie a string to the cart. Tie a mass hanger on the other end of the string. Adjust the pulley so that the string runs parallel to the track.
5Pull the Cart back until the mass hanger reaches the pulley.
6Make a test run to determine how much mass is required on the mass hanger so that the cart takes about 2 seconds to complete the run.
7Record the hanging mass (hanger mass + hanging mass) Table 4.1.
8Pull the Cart back to the initial release position. Set the GLX to v-t graph. Start to record with the motion sensor and release the Cart. Make sure you save each trial.
9Repeat this 5 times with the same mass and record the acceleration values in Table 4.1.
10Repeat [5-9] with additional cart mass (250 gr.)

Name
Partner 1
Department
Date
Partner 2
Data Analysis
1.
Use each v-t graph to calculate the acceleration by fitting a line to the appropriate region on the graph. Record each acceleration on Table 4.1.
2.
Calculate the average acceleration.
3.
Calculate the percent difference between F
Measured
and F
Net
Cart Mass m
1
Hanging
Mass ( m
2)
Trial 1
Measured acceleration
Trial 2 Trial 3 Trial 4 Trial 5
Average acceleration
(m
1
+m
2
)
Table 4.1.
Average acceleration
F measured
=(m
1
+m
2
) a av
F net
= m
2 g % Err( F meas-
F
Net
)
Questions
1Did the results of this experiment verify that F = ma ?
2Why must the mass in F = ma include the hanging mass as well as the mass of the cart?
3What is the origin of the error?
Do your calculations on the back !!