Unit 06 Test Study Guide
Part I. Force and Motion
Review the Unit 05 Study Guide. There are some problems and vocabulary on it that are good study
problems for this test, too.
Part II. Newton’s First Law
1. Explain Newton’s First Law of Motion.
Newton’s First Law of Motion is also known as the Law of Inertia, because it both defines inertia,
and explains its influence on motion. Inertia is the tendency of an object to resist changes in
motion – an object at rest will remain at rest, and an object in motion will remain in motion at a
constant speed and direction, until acted on by an unbalanced force.
Examples: when a car turns the corner or stops quickly, passengers or objects in the car will
continue moving in the original direction until the unbalanced force of the seatbelt, door, or
dash changes the motion.
2. Inertia is an object’s tendency to resist changes in motion. If no outside force is applied to an
object moving at 5 m/s
a. What will happen to its speed over the course of the trip?
The speed will remain constant at 5 m/s unless an unbalanced force acts to change it.
b. What will be its acceleration during the trip?
The acceleration will be 0 m/s/s, because neither the speed nor the direction will change
without an unbalanced force.
3. If a small child is sitting on the handlebars of a bike, and the bike stops suddenly, what will
happen to the child?
c. It continues to move forward. (Because of inertia)
4. What is the name of Newton’s law that explains why the child in problem 3 moves the way it
does when the bike stops?
The Law of Inertia
Part III. Newton’s Second Law of Motion
5. What is the formula that summarizes Newton’s Second Law?
Force = mass x acceleration
6. What causes the force (weight) of an object at rest to increase as its mass increases, if the object
is at rest?
Weight = mass x acceleration of gravity (9.8 m/s/s)
Since weight is a product of mass and the acceleration of gravity, increasing either mass or acc.
Of gravity will increase the product, weight.
Part IV. Newton’s Third Law of Motion
7. What is Newton’s Third Law of Motion called? Explain it.
Newton’s Third Law of Motion is called the Action-Reaction Law. This law says that for every
force exerted, there will be a force that is equal in strength exerted in the opposite direction.
Example: a rocket exerts a force (action force) downward on the ground; the ground exerts an
equal force (reaction force) upward on the rocket.
8. Draw arrows to show the action and reaction forces of a skateboarder making a jump
The skater pushes down on the
ground (action force).
The ground pushes upward on the
skater with equal force (reaction
force).