ISAAC
NEWTON’S
PHYSICS
PRINCIPLES
WHAT NEWTON DID
When it comes to science, Isaac Newton is most famous
for his creation of the THREE LAWS OF MOTION.
The Laws of Motion describe movement of objects in
terms of forces.
These Laws of Motion help explain familiar concepts
such as:
-Forces
-Gravity
-Speed
DO NOW
How would you define a force?
• A push or pull upon an object resulting from the
object's interaction with another object.
Can you think of any real life applications of forces?
• Pulling a wagon
• Kicking a ball
• Pushing a chair
ABOUT
FORCES
Vector quantity
• Magnitude and
direction
May be a contact force
or a field force
THE “NEWTON”
-The Standard unit of force is a
Newton (N)
-The weight of a Newton is
about the weight of an apple.
FUN FACT!
It is rumored that Isaac Newton
designated this weight as the
standard measurement when
the force of Gravity caused an
apple to fall on his head.
FUNDAMENTAL
FORCES
Types
• Strong nuclear force
• Electromagnetic force
• Weak nuclear force
• Gravity
Characteristics
• All field forces
• Listed in order of decreasing strength
NEWTON’S FIRST LAW
OF MOTION
-An object moves with a velocity that is constant in
magnitude and direction, unless acted on by a
nonzero net force
-The net force is the sum of all the forces exerted
on the object
NEWTON’S SECOND LAW
-The acceleration of an object is directly proportional to the net
force acting on it and inversely proportional to its mass.
-m is in kg
-a is in m/s2
WEIGHT
The gravitational force acting on an object of mass
m near the Earth’s surface is called the weight w of
the object
• w = m g is a special case of Newton’s Second Law
• g= 9.8 m/s2
Weight depends upon location
• Ex. Objects have
different weights
on different planets
UNIVERSAL LAW OF
GRAVITATION
Newton discovered that gravity did not only impact people on
earth.
He understood that every particle in the Universe attracts every
other particle with a force that is directly proportional to the
product of the masses and inversely proportional to the square
of the distance between them.
G is the gravitational constant:
NEWTON’S THIRD LAW
If two objects interact, the force exerted by object 1
on object 2 is equal in magnitude but opposite in
direction to the force exerted by object 2 on object
1.
• The action and reaction forces act on different
objects
EQUILIBRIUM
An object either at rest or moving with a constant
velocity is said to be in equilibrium
The net force acting on the object is zero (since the
acceleration is zero)
𝛴𝐹 = 𝑚𝑎=0
SIMULATIONS
http://phet.colorado.edu/en/simulation/forces-andmotion-basics
EXAMPLE
PROBLEM
A force acts on a 2-kg mass and gives it an
acceleration of 3 m/s2. (a) How large is the force? What
acceleration is produced by the same force when
acting on a mass of (b) 1 kg? (c) 4 kg?
Ans. (a) 6 N (b) 6 m/s2: (c) 1.5 m/s2
A)
𝛴𝐹 = 𝑚𝑎
𝑚
𝛴𝐹 = 2 𝑘𝑔 ∗ 3 2
𝑠
𝛴𝐹 = 6 𝑁
B)
𝛴𝐹 = 𝑚𝑎
𝛴𝐹 = 6 𝑁
6 𝑁 = 1𝑘𝑔 ∗ 𝑎
2
𝑎 = 6 𝑚/𝑠
C)
𝛴𝐹 = 𝑚𝑎
𝛴𝐹 = 6 𝑁
6 𝑁 = 4𝑘𝑔 ∗ 𝑎
2
𝑎 = 1.5 𝑚/𝑠
PRACTICE PROBLEMS
1.
An object has a mass of 3 kg. (a) What is its weight on
Earth? On Planet X the acceleration of gravity is 15
m/s². (b) What is the mass of the object on Planet X? (c)
What is the weight of the object on Planet X?
Ans. (a) 29.4 N (b) 3 kg (c) 45 N
A)
𝛴𝐹 = 𝑚𝑎
𝐹 = 𝑚𝑔
2
𝐹 = 3 𝑘𝑔 ∗ 9.8 𝑚/𝑠
𝐹 = 29.4 𝑁
B)
𝑚 = 3𝑘𝑔
C)
𝛴𝐹 = 𝑚𝑎
𝐹 = 𝑚𝑔𝑥
𝑚
𝐹 = 3𝑘𝑔 ∗ 15 2
𝑠
𝐹 = 45 𝑁