SI units, prefixes and checking units

Answer Key - Grade 11 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   A 250 g toy moves at 6 m/s. Using KE = ½mv² in SI units, what is its kinetic energy, Ari?

   4.5 J
2. 2.

   A 150 g toy moves at 2 m/s. Using KE = ½mv² in SI units, what is its kinetic energy, Esme?

   0.3 J
3. 3.

   Pressure = force ÷ area. What is a pascal in SI base units, Kira?

   • kg·m³/s²
   • kg·m/s²
   • kg/(m²·s)
   • kg/(m·s²)
4. 4.

   Momentum = mass × velocity. Which unit fits momentum, Luz?

   • N/s
   • kg·m/s
   • kg·m/s², a newton
   • kg·m²/s²
5. 5.

   Milo says that if an answer's units are right, the answer must be right. Agree or disagree?

   • Agree: matching units mean a right number
   • Agree: milli- means a thousand
   • Disagree: a missing ½ still passes
   • Agree: units can be dropped once the number is found
6. 6.

   Noah says the kilogram, not the gram, is the SI base unit of mass. Agree or disagree?

   • Disagree: a base unit can't carry a prefix
   • Agree: the kilogram is the base unit
   • Disagree: the gram is the base unit
   • Disagree: mass has no base unit
7. 7.

   Pia says 5 m + 3 s = 8. Agree or disagree?

   • Disagree: meters and seconds can't be added
   • Agree: just add the numbers
   • Disagree: it is 15 m·s
   • Agree: the answer is 8 m/s
8. 8.

   A classmate converts 5.0 km/h to m/s as 5.0 × 3.6 = 18 m/s. What went wrong, Ren?

   • Divide by 3.6: about 1.4 m/s
   • km/h and m/s are the same unit
   • Nothing; the units check out
   • Multiply by 1000 and stop
9. 9.

   A classmate writes 4 mm = 4000 m. What went wrong, Tala?

   • Nothing; milli- means a thousand
   • It should be 400 m
   • Milli- is a thousandth: 4 mm = 0.004 m
   • It should be 40 m
10. 10.

    A classmate gets a car's kinetic energy as 1200 kg·m/s. What does the unit show, Zee?

    • It is already in joules
    • v was not squared
    • It should be in newtons
    • Nothing; units don't matter