Coulomb's law: the force between charges

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   Two small spheres carry 20 nC and 30 nC, 10 cm apart. With k = 8.9875 × 10⁹ N·m²/C², what is the force between them in mN, to the nearest hundredth, Ari?

   0.54 mN
2. 2.

   Two small spheres carry 50 nC and 40 nC, 5 cm apart. With k = 8.9875 × 10⁹ N·m²/C², what is the force between them in mN, to the nearest hundredth, Bo?

   7.19 mN
3. 3.

   Two small spheres carry 100 nC and 100 nC, 20 cm apart. With k = 8.9875 × 10⁹ N·m²/C², what is the force between them in mN, to the nearest hundredth, Esme?

   2.25 mN
4. 4.

   How are Coulomb's law and Newton's law of gravitation alike, Jun?

   • Both need the objects to touch each other
   • Both are inverse squares of distance
   • Both use the same constant
5. 5.

   How do the electric and gravitational forces differ in direction, Kira?

   • Electric forces can also repel
   • They are the same
   • Gravity can repel, but electric forces can't
6. 6.

   Two balloons each carry a small charge and a small mass. Which force between them is stronger, Luz?

   • The electric force, by far
   • They are about equal
   • The gravitational force, by far
8. 7.

   Using the table, what force should act at 8 cm, Milo?

   • 9 mN
   • 3 mN
   • 2.25 mN
9. 8.

   Using the table, how does the force change from 2 cm to 6 cm, Noah?

   Use the picture in question 7.

   • It drops by 32 mN each centimeter
   • It drops to one-ninth
   • It drops to one-third
10. 9.

    Using the table's pattern, what force would act at 1 cm, Pia?

    Use the picture in question 7.

    • 144 mN
    • 37 mN
    • 72 mN
11. 10.

    A charged comb picks up small bits of neutral paper. Why, Tala?

    • It shifts the paper's charges
    • The paper is already charged
    • The paper is magnetic