Name _____________
Date ________ Per __
3rd Law, Gravity and Coulomb’s Law Test Review
SHOW ALL WORK FOR CREDIT
1. Newton’s third law of motion involves the interactions of
a. two objects and two forces.
b. one object and one force.
c. one object and two forces.
d. two objects and one force.
2. A leaf falls from a tree and lands on the sidewalk. Identify an action-reaction pair in this situation.
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3. What is the name for equal and opposite forces resulting from the interaction of two objects?
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4. Newton’s 3rd Law of Motion states that
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5. As an object falls toward Earth (it is still in the air),
a.
b.
c.
d.
the object exerts an upward force on Earth.
the object exerts a downward force on Earth.
Newton’s third law does not apply.
the object does not exert a force on Earth.
6. A hammer drives a nail into a piece of wood. Identify an action-reaction pair in this situation.
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7. Describe how Newton’s 3rd Law is involved when a human is walking. _____________________
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8. Describe how Newton’s 3rd Law is involved in an airplane flying. __________________________
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9. Two positive charges 10 m apart are repelled with a force of 100 N. Find the force of repulsion if the same
two charges are now 5 m apart? Show your work.
10. How many times greater will the force of gravity between the Sun and the Earth be if the Earth moves closer,
to 1/5 of its current distance? Show your work.
11. When an astronaut in orbit experiences apparent weightlessness,
a.
b.
c.
d.
the net gravitational force on the astronaut is zero.
the astronaut feels weightless because he or she is free falling.
no forces act on the astronaut.
no gravitational forces act on the astronaut.
12. A repelling force occurs between two charged objects when the charges are _________________.
13. A 29973.33 kg student sits at a desk 2 m away from a 100,000,000 kg student (these students need to lay off the
doughnuts). What is the magnitude of the gravitational force between the two objects?
14. The above graph shows the action-reaction force pair for a football and a football player’s hands catching it.
According to the graph, which force is larger? ________________________________
15. If the player in the above problem is moving away from the ball, but the ball catches up to him and he
catches it, which force is larger? ________________________________
16. Which object will accelerate more, the player or the football? ____________________________
17. When a person is walking forward, what object is pushing them? ________________
18. A box sits on a surface and a normal force holds it up. If the normal force is the “action”, what force is the
“reaction”? _______________________
19. A car hits a brick wall. What is the reaction force? ___________________________________
20. When calculating the gravitational force between two large bodies (like the earth and the moon), you should measure
the distance
a. from the center of one body to the closest point on the other body.
b. from the center of each body.
c. from the closest points on each body.
d. from the most distant points on each body.
21. Why does an astronaut weigh less on the moon than on Earth? ________________________________
22. In the diagram shown above, the circles represent small balls that have electric charges. Ball 1 has a negative charge,
and ball 2 is repelled by ball 1. What is the electric charge on ball 2? (positive or negative) _________
23. An attracting force occurs between two charged objects when the charges are ______________________.
24. Which equation expresses Newton’s law of universal gravitation?
25. If the moon was suddenly pushed twice as far from the earth as it is now (by a large asteroid smashing into it), the
gravitational force between the earth and the moon would be _______________________.
26. If the mass of the moon was suddenly doubled by a large asteroid landing on it, the gravitational force between the
earth and the moon would be __________________________.
27. Two negative charges are repelled from each other by a force of 8 N. If the distance between then is doubled, the
electric force will be (HINT: It helps to draw this.)
28. Two positive charges are repelled from each other by a force of 8 N. If the charges are moved to half the original
distance (i.e., they are now closer together), the electric force will be (HINT: It helps to draw this.)
29. Two electric charges (q1 = -1.4222 C, q2 = -5 C) are separated by 2,000 m. Find the force between them.
Round to the nearest whole number.
30. Two electric charges (q1 = +1.4222 C, q2 = -5 C) are separated by 8 ,000 m. Find the force between them.
Round to the nearest Newton.
31. When Newton first thought of gravity as a force, what explanation did he offer for why the moon does not
fall to the Earth? ___________________________________________________________________
32. What is necessary for a hypothesis to become a theory? _____________________
33. What evidence did Newton find to support his hypothesis? ___________________
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34. String theory is a model in theoretical physics which predicts particles in other dimensions. No such particles
have yet been observed. Should we accept string theory as scientific fact? Explain why or why not?
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