Units and Powers of 10

Post-Test

  1. In the metric system, what are the basic units of length, mass, time, and electrical charge?

    length = meters
    mass = grams
    time = seconds
    charge = coulombs

  2. Answer the following questions about the metric system
    1. How many centimeters are in a meter?
      There are exactly 100 centimeters in a meter.
    2. How many meters are in a kilometer?
      There are exactly 1000 meters in a kilometer.
    3. How many milligrams in a gram?
      There are exactly 1000 milligrams in a gram.
    4. How many microseconds in a second?
      There are 1,000,000 microseconds in a second.
    5. How many watts are in a Megawatt?
      There are 1,000,000 watts in a Megawatt.
    6. How many centimeters are in a kilometer?
      There are 100 centimeters in a meter and 1000 meters in a kilometer,
      so there are (1 kilometer) X (1000 m/km) X (100 cm/m) = 100,000
      centimeters in a kilometer.

  3. Answer the following, given the information in the table below.

    1. How many inches are in a meter?
      1 meter X (100 centimeters/meter) X (1 inch/2.54 cm) = 39.37 inches
      or
      1 meter X (1.0936 yards/meter) X (36 inches/yard) = 39.37 inches

    2. How many yards are in a kilometer?
      1 kilometer X (1000 meters/kilometer) X (1.0936 yards/meter) = 1094 yds
      or
      1 kilometer X (0.6214 miles/kilometer) X (5280 feet/mile)
      X (1 yard/3 feet) = 1094 yards

    3. How many inches in a kilometer?
      1 kilometer X (1000 meters/kilometer) X (1.0936 yards/meter)
      X (36 inches/yard) = 39370 inches
      or
      1 kilometer X (0.6214 miles/kilometer) X (5280 feet/mile)
      X (1 yard/3 feet) X (36 inches/yard) = 39370 inches

    4. How may feet in a meter?
      1 meter X (1.0936 yards/meter) X (3 feet/yard) = 3.28 feet

  4. The average distance between the Earth and the Sun is about 150 million kilometers. How far is that in meters? In miles? In feet?

    150,000,000 kilometers X (1000 meters/kilometer) = 150,000,000,000 meters
    150,000,000 kilometers X (0.6214 miles/kilometer) = 93,210,000 miles
    93,210,000 miles X (5280 feet/mile) = 492,148,800,000 feet

  5. The floor of a room measures 40 feet by 30 feet. How many square feet of carpet is required to cover it? How many square yards? How many square meters?

    Area = 40 feet X 30 feet = 1200 ft2
    Area = (40 feet X 1 yard/3 feet) X (30 feet X 1 yard/3 feet) = 133.3 yd    2

    Convert the dimensions to meters:
    40 feet X (1 yard/3 feet) X (1 meter/1.0936 yards) = 12.2 meters
    30 feet X (1 yard/3 feet) X (1 meter/1.0936 yards) = 9.14 meters
    Area = 12.2 meters X 9.14 meters = 111.5 m    2

  6. Electric field is measured in N/C. What is one of the formulas for electric field, based on these units?

    Force is measured in newtons (N) and electrical charge is measured in coulombs.
    Therefore we could guess that Electric Field = Force / Charge = F/Q = E

  7. The basic unit of pressure is the pascal. If the formula for pressure is

Pressure = Force / Area

and force is measured in newtons, or kg m/s2, and area is measured in m2, then what is a pascal, expressed in basic units of length, mass, and time?

We could guess that the units of pressure would be (kg m/s2) / (m2). This then becomes (kg m/s2) X (1/m2) = (kg m)/(m2s2) = (kg /ms2). However, this is usually expressed as N/m2 (to remind us that pressure = force/area) or simply pascals.

If you missed more than one or two questions on this post-test, and are not sure why you missed them, you may want to go back and view the relevant parts of the units tutorial. Otherwise, you can return to the main menu and look at another tutorial!

Questions? Ask the designer, Jim Heath

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