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What is Mass and Force Practice Problems

By — McGraw-Hill Professional
Updated on Oct 25, 2011

What is Mass and Force Practice Problems

Review the concept of mass at What is Mass and Force Help

Practice 1

Suppose you place an object in a mass meter similar to the one shown in Fig. 15-1. Also suppose that the mass-versus-frequency calibration graph looks like Fig. 15-2. The object “see-saws” at a rate of 5 oscillations per second (that is, a frequency of 5 Hz). What is the approximate mass of this object?

How Things Move HOW MASS IS DETERMINED

Fig. 15-1. Mass can be measured by getting an object to “see-saw” between a pair of springs in a weightless environment.

How Things Move HOW MASS IS DETERMINED

Fig. 15-2. Graph of mass versus oscillation (“see-sawing”) frequency for a spring-type mass meter.

Solution 1

Locate the frequency on the horizontal scale. Draw a vertical line (or place a ruler) parallel to the vertical (mass) axis. Note where this straight line intersects the curve. Draw a horizontal line from this intersection point toward the left until it hits the mass scale. Read the mass off the scale. It is approximately 0.8 kg, as shown in Fig. 15-3.

How Things Move HOW MASS IS DETERMINED

Fig. 15-3 . Solution to Practice 1.

Practice 2

What will the mass meter described in Practice 1 do if a mass of only 10 grams (10 g) is placed in between the springs?

Solution 2

The scale will oscillate much faster. We don’t know exactly how fast, because 10 g is only 0.01 kg, which is too small to show up on the graph in Fig. 15-2.

Practice 3

Wouldn’t it be easier, and more accurate in real life, to program the calibration curve for a mass meter into a computer, instead of using graphs like the ones shown here? That way, we could simply input the “see-saw” frequency into the computer, and read the mass on the display.

Solution 3

Yes, that would be easier. In a real-life mass meter of the sort we’ve been discussing here, that would be done. In fact, we should expect such a scale to have a built-in microcomputer and display to tell us the mass directly.

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