LAB: NEWTON ’s FIRST LAW

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HOW MASS IS RELATED TO INERTIA ?

 

Newton’s first law states that an object at rest to remain at rest, while an object in motion tends to remain in motion. This property of matter is called inertia.

 

An inertia balance is a device that makes use of this property to determine the mass of an object. The period of an inertia balance is directly related to the amount of mass attached to the balance. The period is the amount of time it takes for one complete swing of the balance.

 

PURPOSE: You will learn how an inertia balance is used to determine mass. You will find the mass of an object using your inertia balance. Then you will check your measurement.

 

SKILLS: observing, measuring, graphing

 

MATERIALS: inertia balance, masses (5) , graph paper, stopwatch, masking tape, C-clamp, unknown mass (2)

 

 

PROCEDURE

 

1. Clamp the inertia balance to the ring stand so that it can swings freely.

2. Measure: Secure a 305g mass to the balance. Pull the mass back 5-8cm back and release it. Time 10-swings of the balance. Record your time in table 1.

3. Repeat step 2  for 325 , 355, 375, and 400g masses. Then repeat step 2 for the 1 unknown  mass.

4. Calculate the period by using the formula: period = time for 10 swings / 10

Record the period and the period squared for each mass in table 1.

5. Hang your unknown mass and record the period and the period squares.

 

T unknown mass = _____________________ T² ____________________

 

6:  graph: Make a graph of period squared vs mass for the 5 known masses.

That means: x = mass and y = (period)^2. You may want to multiply your period by 10 to make it easier to graph. Trace the best fit line.

 

TABLE 1:

                                                                                

 

ANALYSIS

 

7. Compute the equation of the line. Y= mx + b   :You need to find the slope (m) and

the y-intercept (b).

 

8. Using the equation of the line, find the mass of your object. You are solving for y (mass) and you are given x (the period² for the unknown mass)

 

Unknown mass measured = ____________________________

 

 

9. Find out the true mass of the unknown mass using a spring scale.

 

 

True mass = ____________________________

 

 

Are you close? 

 

 

10) An object on the balance makes 15 swings in 10 seconds. What is the period of the balance ?

What is the mass of the object ? (use your equation found in 7)