Equilibrium and Newton's First Law · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Still means balanced

Mathematics · Mechanics · ages 17-18
Name ______________________   Date ____________

  1. Forces of 5 N east, 5 N west and 4 N north act on a ring. Tom says they are in equilibrium. Is Tom right?

    Circle one:   True   False

  2. A 6 N force pulls east and an 8 N force pulls north on a small ring. What size of third force, in N, puts the ring in equilibrium?

    Answer: ______________

  3. A 6 N force pulls east and an 8 N force pulls north on a small ring. What size of third force, in N, puts the ring in equilibrium?

    Answer: ______________

  4. A book rests on a table. Which pair correctly names every force on the book and what exerts it?

    • Gravity plus the push of the book on the table
    • Only the normal force
    • Gravity from Earth and a normal force from the table

  5. A 10 kg mass hangs at rest from a single vertical string. Take g = 10 N/kg. What is the tension?

    • 100 N
    • 10 N
    • 50 N
    • 1000 N

  6. Forces of 5 N east, 5 N west and 4 N north act on a ring. What single extra force puts it in equilibrium?

    • 4 N south
    • 4 N north
    • 10 N south

  7. A 6 kg mass hangs at rest from two vertical strings sharing the load equally. Take g = 10 N/kg. What is the tension in each string, in N?

    Answer: ______________

  8. A 6 kg mass hangs at rest from two vertical strings sharing the load equally. Take g = 10 N/kg. What is the tension in each string, in N?

    Answer: ______________

  9. Lee says a book on a table feels only gravity pulling down. What is missing?

    • Nothing: gravity acts alone
    • The normal push up from the table
    • The weight of the table

  10. A puck glides across ice in a straight line at steady speed. Amy says the horizontal forces on it are balanced. Is Amy right?

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Still means balanced W1-mt_e6RFRQkRPo-s1

  1. False · East and west cancel but the 4 N north is unbalanced, so the ring is not in equilibrium.
  2. 10 · The first two give a 10 N resultant, so the balancing force must be 10 N the opposite way.
  3. 10 · The first two give a 10 N resultant, so the balancing force must be 10 N the opposite way.
  4. Gravity from Earth and a normal force from the table · Only gravity and the normal force act on the book itself.
  5. 100 N · Tension balances the 100 N weight, so it is 100 N.
  6. 4 N south · East and west cancel, leaving 4 N north to kill with 4 N south.
  7. 30 · The weight is 60 N, so each string carries half: 30 N.
  8. 30 · The weight is 60 N, so each string carries half: 30 N.
  9. The normal push up from the table · At rest the table pushes back up, balancing gravity exactly.
  10. True · Steady velocity means zero net force by the first law, so horizontal forces balance.
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