PhysicsLAB Lab
Gravitational Field Strength

Background
 
In this lab we are going to measure the local gravitational field strength of the Earth in our classroom. We will need to make three measurements: the object's weight, its gravitational mass, and the rate at which is gains speed as it falls to the floor.
 
The equipment needed will include: a triple beam balance, a spring scale, a motion detector and it supporting computer-assisted software.
 
I suggest collecting data as a class activity.
 
Part I. Trials and Data Table
 

item's
gravitational mass spring scale weight ratio of weight/mass slope of vel-time graph
trial description (kg) (N) (N/kg) (m/sec/sec)
1
2
3
4
5
6
7
8
 
 
Part II. Graph Shape Stetches
 
From the following graphs, select two answers. One to represent the general shape of the position vs time graphs that were displayed for each trial; and two, the general shape of the velocity vs time graphs that were displayed for each trial.
 
Conclusions
 
1. Calculate the average value of the column entitled Weight/Mass. This will later be referred to as average1

2. Calculate the average value of the column entitled Slope of Velocity vs Time. This will later be referred to as average2

Open EXCEL and plot a graph of Weight vs Mass. This title means that you are to place Mass (kg) on the x-axis and Weight (N) on the y-axis. When all of the data has been graphed, add a trend line (line of best fit) and answer the following questions.
3. What is the slope of the trend line? 

4. What are units of the slope?
 
5. What is the y-axis intercept of the trend line? 

6. Discuss the reasonableness of your graph's y-axis intercept. What would have been its "perfect value?"
 

Choose the correct comparison between the average of the Weight/Mass column (average1), the average of the slope of velocity-time column (average2) and the slope of your EXCEL graph.
7. To within two significant figures, how do the numerical values of average1 and average2 compare to each other?
 
8. To within two significant figures, how does average1 compare to the slope of your EXCEL graph of Weight vs Mass?
 
9. To within two significant figures, how does average2 compare to the slope of your EXCEL graph of Weight vs Mass?
 
10. True or False. Another method of measuring the local gravitational field strength is to measure the acceleration due to gravity for freely falling bodies
 
11. True or False. A bowling ball and baseball will strike the ground at the same time if released from the same height simultaneously.
 
12. Explain your reasoning for your previous choice.
 





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