Transcript Activity 79 Analysis Questions 1. a. b. Describe the changes in direction and speed of the marble when they’re inside the circular track? The marbles’ direction changed.

Activity 79 Analysis Questions
1.
a.
b.
Describe the changes in direction and speed of the
marble when they’re
inside the circular track?
The marbles’ direction changed constantly inside the
circular track because of the force the wall exerted on
the marble. Similarly, the surface of the circular track
rubbed on the marble and slowed in down slightly.
outside of the circular track?
The direction once outside the circular track was in a
straight line, moving across the table as shown on
Transparency 79.1, “Inertia Diagrams”. The speed
slowed slightly because of the table surface rubbing on
the marble.
2. Describe any changes in the path of the
marble that occurred when you changed the
a. opening position of the circular track.
The marble left the opening in a different
direction for each opening position. Once it left
the circular track, however, it continued in a
straight line.
• mass of the marble.
When comparing the glass (lighter) marble to
the heavier (metal) one, no changes occurred
to the direction that the marble traveled.
3. Imagine that a car is approaching a curve in the
road when it suddenly loses its steering and
brakes. The area is flat and there is no guardrail
on the road.
a. Copy the diagram below in your science
notebook. Then draw a line showing the car’s
path when it loses its steering and brakes.
b. Explain why the car will take that path.
Because of inertia, which in the absence
of other forces keeps moving objects
moving in a straight line.
c. How would your answer change if the car
had more mass? Explain.
More mass will not change the direction
the car travels. It would, however, affect
the force needed to stop the car.
Activity 79 Major Concepts
• An object that is not being subject to a
force will continue to move at a constant
speed in a straight line.
On your next blank page, take notes
Force Notes
Net Force
• In many situations, including driving, more
than one force is acting on an object.
• The combination of all forces acting on an
object is the net force.
• Net force determines whether, and by how
much, an object’s motion is changed.
• Total Force
Force Diagrams
• Objects are shown as a rectangle or
square.
Force Diagrams
• A push or pull (force) is shown with an
arrow
Force Diagrams
• The arrow always points AWAY from the
object.
Force Diagrams
• The bigger the force, the bigger the arrow
Force Diagrams
• Label the arrows with the magnitude
(amount) of the force (in N)
3N
10 N
Force Diagrams
• Net Force is the sum of all of the forces
3N
10 N
7N
Practice:
• Draw an object with two forces acting in
opposite directions with one force equal to
2 N and one force equal to 8 N.
Force Diagrams
2N
8N
Net Force
• Draw the net force acting on this object.
2N
8N
Force Diagrams
Net Force
6N
Balanced vs. Unbalanced Forces
• If there is a situation of unbalanced forces,
there is a net force.
• Balanced forces mean there is a net force of
zero on the object.
• Describe the motion of the blocks below.
2N
10 N
A.
8N
B.
8N