Newton’s First Law Notes
Force:
• A push or pull
More than one force can act on an object at the
same time.
Net Force:
• Combination of all forces acting on an object.
Net force means total force.
The net force on an object determines how the
motion of an object changes.
Balanced Force
• two or more forces
whose effects cancel
each other out and do
not change the motion
of an object.
Unbalanced Force
• two or more forces
acting on an object that
do not cancel, and
cause the object to
change its motion.
• net force is zero
• net force is not zero
Force Diagrams:
• Forces are represented by using arrows.
• The larger the arrow the larger the force.
• The smaller the arrow the smaller the force.
1. What is Newton’s first law of motion?
• If the net force acting on an object is zero, the
object will remain at rest or move in a straight
line with a constant speed.
• An object at rest will stay at rest, an object in
motion will stay in motion unless it is acted
upon by an unbalanced force.
2. The motion of an object doesn’t change until
an unbalanced force acts on it.
Newton’s First Law
Newton’s First Law
Newton’s First Law
Newton’s First Law
Newton’s First Law
Spring Scale
• Measures weight
• Unit of measurements:
– Newtons (N)
• 1 newton = 100 grams
– Pounds
– Kilograms, grams
• Weight is a measure of the force of gravity on
an object.
Dates To Remember
• Monday, January 9
– Forces Test
• Tuesday, January 10
– ALL project grades and improvement to project
grades are done.
– Project grades lower than 48 points can be
improved.
– If you do not see me to grade your project it will
be a zero
• Friday, January 20
– Last day of the nine weeks
Review Questions
1. What is a force? Net force?
2. Is this object balanced? What is the net
force?
15 N
10 N
1. What is Newton’s first law of motion?
3. What is friction? Give an example.
• A force that acts to oppose sliding between
two surfaces that are touching. Examples: air,
water, roads, etc.
4. What do different forms of friction have in
common?
• Different forms of friction always slow an
object down.
5. Is friction a force? Explain.
• Yes, it causes moving objects to slow down
and prevents stationary objects from moving
if a force is applied to them.
6. In terms of friction and force, how can an
object keep moving?
• To keep an object moving, a force has to be
applied to overcome the effects of friction.
7. If friction did not exist, describe the motion of
any object once an unbalanced force is
applied to that object.
• An object in motion would continue to move
in a straight line with a constant speed.
Example of Low Friction
Example of Low Friction
Example of Low Friction
8. What are the three types of friction?
Describe each.
• Static Friction – surfaces stick together where
they are in contact; due to the attraction
between the atoms on the two surfaces; no
movement by an object.
• Sliding Friction – when a moving object slows
down as it slides across an object; due to the
roughness of a surface.
• Rolling Friction – when an object rolls across a
surface.