Units and Prefixes Practice Questions

Review these concepts at: Units and Prefixes Study Guide

Practice Questions

1. You want to measure the volume of your microwave oven. What do you need and how do you proceed? Is volume a fundamental or a derived quantity?
2. We define the density of a substance as the mass of the unit volume of that substance. Would the density unit be a fundamental or a derived unit?
3. When you buy a lightbulb at the store, you may choose one that is rated at 25W, 60W, lOOW, and so on. Is this a good measure for the light you get from your bulb? Remember, a good unit is accessible, universal, and reproducible. Why do you think some manufacturers of"eco-bulbs" use units such as lumens on their packaging when they advertise their bulbs?
4. The radian is the angle spanned on a circle's circumference by an arc of length equal to the radius of that circle. Look at Figure 1.2 and decide if this angular measure is a fundamental quantity?

Use the conversion factors to work the following practice problems.

5. If you are to measure the mass of the earth, you will end up with 5.98 . 10²⁴ kg. Find the mass in pounds and in ounces.
6. How many liters of engine oil do you need to buy if your car engine capacity is 3.5 quarts?
7. A room is 10.0 feet long by 8.5 feet wide. What is the area of the room in m²?
8. In the previous practice problem, the room is 12 feet tall. What is the volume in m³?
9. What is the SI unit for temperature? What is the unit for mass?
10. How many ounces of pudding are there in a 300gram serving? Use the fact that 1 pound has 16 ounces.
11. You buy a European car that uses 14 liters of gas for 100 kilometers. How many gallons of gas do you need to travel 62.1 miles?
12. In problem 12, how many miles can your car go using just one gallon of gas?

13. The root word centi means 100 in which language?
    1. Greek
    2. Latin
    3. Spanish
14. Which metric prefix means one-thousandth?
    1. kilo
    2. centi
    3. milli
15. A time of 5 milliseconds is equal to which of the following?
    1. 0.0005 s
    2. 0.005 s
    3. 0.05 s
16. Twenty-five kilometers is equal to which of the following?
    1. 250,000 m
    2. 25,000 m
    3. 250 m
17. What do you call 2.5 × 10³ kg of steel?
    1. 250,000 g
    2. 25,000 g
    3. 2.5 tons
18. 1 × 10^–3 kg is equal to which of the following?
    1. 1 milligram
    2. 1 gram
    3. 1 milikilogram
    4. all of the above

19. You have an electronic balance with a five-digit display, and you measure a crucible to have a weight of 5.2546 g. Then, using the same balance, you measure the oven that will be used to heat up that crucible and find that it is 78.236 g. What is the mass of the crucible and oven assembly?
20. What factor is limiting your precision in the case of the previous problem measurements?
21. You measure the size of your microwave oven to be 28.6 cm × 27.9 cm × 20.8 cm. What is the volume of the oven in cm³? How many significant figures does your result have?
22. The voltage across one of the elements of a voltage divider is 97.2 volts and is 13.758 volts across the other element. What is the result of adding these two voltages together? How many significant figures does the result have?
23. Assume that 1 pound has an exact mass of 453.59237 g. To three significant figures, this is which of the following?
    1. 453.6 g
    2. 454 g
    3. 0.45359 kg
24. Assume that 1 pound has an exact mass of 453.59237 g. To two significant figures, this is equal to which of the following?
    1. 453 g
    2. 454 g
    3. 0.45 kg

25. Write the following numbers in scientific notation:
    1 kg = 0.6852 slug
    1 mi/h = 1,609 m/h
    1N = 0.2448 lb
    Planck's constant = 0.0006626 . 10–30 J. s
    Acceleration due to gravity = 32.2 ft/s²
    Sun's mass = 199· 10²⁸ kg
    Acceleration due to gravity = 32.2 ft/s²
26. Is it true that if you use scientific notation, you do not have to worry about significant figures? Explain briefly.
27. The atomic mass of the chemical element niobium (Nb) is 92.90638 u. Convert this mass into kilograms using only three significant figures. Use scientific notation to express your answer.