Name___________________________________________ Period_______ Date_________
CONCEPTUAL PHYSICS ALIVE! VIDEO QUESTION SET
Newton’s Third Law
In this lecture, Paul Hewitt describes the nature of interaction: how two objects interact with equal
and opposite force. He gives several examples, and explains why equal forces don’t always produce
equal consequences. Read the following questions before the presentation begins. Answer them
while the presentation is in progress. [43 minutes]
1. When Hewitt leans against the wall,
everyone can see that he’s pushing the wall.
Those who understand physics see something
else going on, too. What is it?
2. When the big block and the little block are released,
A. the big block moves farther.
B. the little block moves farther.
C. both blocks move equal distances.
3. When the big block and the little block are released,
A. the big block pulls with greater force.
B. the little block pulls with greater force.
C. both blocks pull with equal force.
4. Which is the greater force in the tug-of-war demonstration?
A. Hewitt on Helen
B. Helen on Hewitt
C. same for both
5. If A pulls on B, then
B pulls on A.
6. If you want to swim forward, you must
push water backward.
X
7. __True
or __False: The road pushes cars forward.
Conceptual Physics Alive! Video Question Sets © Dean Baird. All rights reserved.
• 19 •
8. The winner of a tug-of-war is the person or team that
A. pulls harder on the rope.
B. pushes harder on the ground.
9. To make the reading on the bathroom scale more to his liking, Hewitt
A. pulled up on the sink to increase the reading on the scale.
B. pushed down on the sink to increase the reading on the scale.
C. pulled up on the sink to decrease the reading on the scale.
D. pushed down on the sink to decrease the reading on the scale.
10. A ball of clay is pulled down by “the force of gravity.” What is the reaction
force in this case?
The ball pulls up on Earth.
11. Use “proportionally-sized symbols” to show why the acceleration of the
ball is greater than the acceleration of the Earth. (Write the appropriate
equations with large or small symbols as Hewitt does.)
a =F
m
a
=F
m
12. Repeat the process to show what happens when a bullet is fired from a rifle.
a
a =F
=F
m
m
13. Write the interaction involved in the thrust of a rocket.
the exhaust gas
The rocket
______________________________
pushes down on ______________________________.
the rocket
The exhaust gas
______________________________
pushes up on ______________________________.
Conceptual Physics Alive! Video Question Sets © Dean Baird. All rights reserved.
• 20 •