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11th grade Coulomb's law: the force between charges worksheet

6 printable versionsChallenge Me10 questions · answer keyFree · no account

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Coulomb's law: the force between charges

Grade 11 Science Worksheet - Challenge Me

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

  1. Two small spheres carry 40 nC and 40 nC. With k = 8.9875 × 10⁹ N·m²/C², how far apart in cm must they be for a force of 3.6 mN, to the nearest hundredth, Ari?

  2. Two small spheres carry 10 nC and 90 nC. With k = 8.9875 × 10⁹ N·m²/C², how far apart in cm must they be for a force of 0.9 mN, to the nearest hundredth, Bo?

  3. Two small spheres carry 80 nC and 50 nC. With k = 8.9875 × 10⁹ N·m²/C², how far apart in cm must they be for a force of 10 mN, to the nearest hundredth, Esme?

  4. A positive charge sits between two equal positive charges, closer to the left one. Which way is the net force on it, Kira?

    • Zero, since the charges are equal
    • To the right, away from the nearer charge
    • To the left, toward the nearer positive charge

  5. Milo says a +10 nC sphere pushes harder on a +2 nC sphere than the +2 nC sphere pushes back. Agree or disagree?

    • Agree: bigger charges push harder
    • Disagree: the two forces are equal
    • Agree: the small one barely pushes

  6. Noah says a charged balloon pulls on a wall harder than the wall pulls on the balloon. Agree or disagree?

    • Agree: the charged one pulls harder
    • Agree: walls can't pull
    • Disagree: they pull on each other equally

  7. Pia says the force between two charges disappears completely once they are 1 m apart. Agree or disagree?

    • Disagree: it gets weaker but isn't zero
    • Agree: forces stop at 1 m
    • Agree: charges can't reach that far

  8. Both charges double, and the distance between them doubles too. What happens to the force, Ren?

    • It stays the same
    • It doubles
    • It is 8 times as big

  9. The distance between two charges triples. What fraction of the force is left, Tala?

    • One-sixth
    • One-ninth
    • One-third

  10. One charge triples, and the distance triples. What happens to the force, Zee?

    • It drops to one-third
    • It triples
    • It stays the same
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11th grade Coulomb's law: the force between charges worksheet – printable
Print: 123456

About this worksheet

Coulomb's law: the force between charges. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can use F = kq₁q₂ ÷ r² with k = 8.9875 × 10⁹ N·m²/C², with charges in nC, distances in cm and forces in mN.
  • I can scale forces. Each charge counts once, while distance counts squared: twice as far gives one-quarter, and half as far gives 4 times. I can find the distance that gives a chosen force.
  • I can say that like charges repel and unlike attract, with equal and opposite forces. I can add forces from neighbors in a line.
  • I can compare Coulomb's law with gravity: both are inverse squares, but only electric forces repel, and electric forces are far stronger.

Standard: HS-PS2-4

Words to know

Coulomb's law: F = kq₁q₂ ÷ r², the force between two charges

k: Coulomb's constant: 8.9875 × 10⁹ N·m²/C²

inverse square: The force falls as 1 ÷ distance²

nanocoulomb (nC): 10⁻⁹ coulombs, a typical charge for a rubbed balloon

net force: The total of all forces on an object, with directions

Common mistakes

Your child divided by the distance factor, not its square. Coulomb's law is an inverse square: twice as far, one-quarter the force.

Your child did not square the distance. F = kq₁q₂ ÷ r².

Your child left out the square root. Rearranging F = kq₁q₂ ÷ r² gives r = √(kq₁q₂ ÷ F).

Questions parents ask

What is the most common mistake with coulomb's law: the force between charges?

Your child divided by the distance factor, not its square. Coulomb's law is an inverse square: twice as far, one-quarter the force.

Are these 11th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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