Download Newtons Laws of Motion Notes

Newton’s Laws of Motion - Notes
Net Force
I. A force is a push or pull that one object exerts on another object.
Force is measured in Newtons (N).
II. Objects have more than one force acting on them.
III. Net force is the total force.
A. When net force = 0, forces are balanced.
B. When net force ≠ 0, forces are unbalanced.
Newton’s First Law of Motion
IV. All objects have a natural tendency to resist changes in motion called
inertia.
A. Inertia causes objects to remain constant in terms of speed and
direction.
V. Newton’s 1st Law of Motion
A. Law of Inertia
B. The velocity of an object will remain constant unless an
unbalanced force acts on it
VI.Inertia
A. Depends on mass
B. The greater the mass of an object, the greater the inertia the
object has.
C. Great inertia means:
1. harder to slow down
2. harder to speed up
3. harder to change direction
4. harder to start moving when the object is at rest
D. Inertia depends on:
1. mass
2. not affected by gravity or lack of gravity
a) in empty space (a vacuum) objects have inertia that is
proportional to their mass.
Newton’s Second Law of Motion
VII.Acceleration causes objects to:
A. speed up
B. slow down
C. change direction
VIII.Newton’s 2nd Law of Motion
A. When an unbalanced force acts on an object, the object will
accelerate in the direction of that force.
B. summarized as F = ma
1. F → force (in newtons)
2. m → mass (kg)
3. a → acceleration (m/s2)
C. Three main ideas:
1. Acceleration is the result of unbalanced forces
2. Acceleration is proportional with force
3. Acceleration is inversely proportional with mass
D. What does proportional and inversely proportional mean?
Proportional
Inversely Proportional
Force Mass Acceleration
Force Mass Acceleration
1N
1 kg
1 m/s2
1N
1 kg
1 m/s2
2N
1 kg
2 m/s2
1N
0.5 kg
2 m/s2
1/2 N
1 kg
0.5 m/s2
1N
2 kg
0.5 m/s2
Newton’s Third Law of Motion
IX.Newton’s 3rd Law of Motion
A. Law of Action and Reaction
B. When one object exerts a force on the first that is equal in
magnitude and opposite in direction.
1. Forces always come in pairs.
2. Action and reaction forces act on different objects.
X. Newton’s third law also explains why rockets are pushed upward into
space. When the fuel is burned, the gases exert a downward force,
thereby exerting an equal and opposite upward force on the rocket