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 GRAVITATIONNewton 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

EQUILIBRIUMAn 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)

=0

SIMULATIONS

http://phet.colorado.edu/en/simulation/forces-and-motion-basics

EXAMPLEPROBLEM

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)

B)

C)

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

PRACTICE PROBLEMS1.

A)

B)

𝑚=3𝑘𝑔

C)