Name _____________
Date ________ Per __
3rd 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.
c. one object and two forces.
b. one object and one force.
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.
____
3. What is the name for simultaneous equal but opposite forces resulting from the interaction of two objects?
____
4. Newton’s 3rd Law of Motion states that
____
5. As an object falls toward Earth (it is still in the air),
a. the object exerts an upward force on Earth.
b. the object exerts a downward force on Earth.
c. Newton’s third law does not apply.
d. 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.
7. Describe how Newton’s 3rd Law is involved when a human is walking. _____________________
____________________________________________________________________________________
____________________________________________________________________________________
___________________________________________________________________________
8. Describe how Newton’s 3rd Law is involved in an airplane flying. __________________________
____________________________________________________________________________________
____________________________________________________________________________________
___________________________________________________________________________
9. 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? ________________________________
10. 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? ________________________________
11. Which object will accelerate more, the player or the football? ____________________________
12. When a person is walking forward, what object is pushing them? ________________
13. 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”? _______________________
14. A car hits a brick wall. What is the reaction force? ___________________________________
Gravitation & Electric Force Test Review
____
____
____
____
____
____
____
____
1. 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.
2. Why does an astronaut weigh less on the moon than on Earth? ________________________________
3. 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) _________
4. An attracting force occurs between two charged objects when the charges are ______________________.
5. Which equation expresses Newton’s law of universal gravitation?
6. 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 _______________________.
7. 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 __________________________.
8. 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.)
____ 9. Tides are caused by ______________________.
____ 10. 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.)
____ 11. When an astronaut in orbit experiences apparent weightlessness,
a. the net gravitational force on the astronaut is zero.
b. the astronaut feels weightless because he or she is free falling.
c. no forces act on the astronaut.
d. no gravitational forces act on the astronaut.
____ 12. A repelling force occurs between two charged objects when the charges are _________________.
13. A 61.5 kg student sits at a desk 3.78  10 m away from a 9.3  10
gravitational force between the two objects?
kg galaxy. What is the magnitude of the
14. Two electric charges (q1 = 1.4222 x 10-6 C, q2 = 5 x 10-9 C) are separated by 2 x 10 -4 m. Find the force
between them. Write your answer in standard notation, and round to the nearest Newton.
15. Two electric charges (q1 = 1.4222 x 10-6 C, q2 = 5 x 10-9 C) are separated by 8 x 10 -4 m. Find the force
between them. Write your answer in standard notation, and round to the nearest Newton.
16. Two point charges having charge values of 2.0 x 10-6 C and –4.0 x 10-6 C, respectively, are separated by
0.015 m. What is the value of the mutual force between them?
17. A 61.5 kg student sits at a desk 1.25 m away from a 70 kg student. What is the magnitude of the
gravitational force between the two students?
18. a. What is the electric force between an electron (q1 = -1.6 x 10-19 C) and a proton (q2 = 1.6 x 10-19 C) that
are separated by a distance of 1.0 x 10-10 m?
b. Is the force attractive or repulsive? ________ How do you know? ________________________
19. When Newton first thought of gravity as a force, what explanation did he offer for why the moon does
not fall to the Earth? ________________________________
_________________________________________________________________
20. What is necessary for a hypothesis to become a theory? _____________________
21. What evidence did Newton find to support his hypothesis? ___________________
___________________________________________________________________
22. 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? ________________________________________________________________________
23. 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.
24. 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.
25. What is the force of gravity between a mass of 9.11 x 10 kg (an electron) and a mass of 1.67 x 10
kg (a proton) that are separated by a distance of 2.0 x 10 11 m (the radius of an atom)? Show your work.
26. What is the force of gravity between a supermassive black hole with mass 3.6 x 10 40 kg and a smaller
(but still supermassive) black hole with mass 4 x 1037 kg when they are 1.5 x 1011 m apart? (This is how
far apart the Earth and the Sun are.) Show your work.