# Forces and Newton.

## Presentation on theme: "Forces and Newton."— Presentation transcript:

Forces and Newton

A Force is a push or a pull.
Forces A Force is a push or a pull. Examples include Gravity Contact Force Friction Magnetic force Electrical force

Balanced or Unbalanced
Forces can be Balanced or Unbalanced Which side will win?????

Video Clips Play Push and Pull clip – 3:14

do NOT change the object’s motion
Balanced Forces do NOT change the object’s motion

Unbalanced Forces cause objects to
Start moving Stop moving Change direction

Unbalanced Forces When in the opposite direction, the box moves the direction of the larger force.

The amount of force used to move an object.
WORK The amount of force used to move an object. Work is done anytime force causes an object to move. Work is not done when there is no motion.

Quiz A push or pull is called a ______
When two equal forces are acting on an object in opposite directions they are _________ forces When forces are unequal they are _________ forces. Forces are described in strength and ________ Force Direction Balanced Unbalanced

Sir Isaac Newton ( ) His ideas are built upon the ideas of Galileo. Newton's three Laws of Motion are general, universal LAWS that explain a wide range of situations. (Newton also invented Calculus and the reflecting telescope).

1st Law of Motion (Law of Inertia)
An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

1st Law Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. These pumpkins will not move unless acted on by an unbalanced force.

How can the person become part of the car?
The car hits the wall and stops, but the person keeps on going because he is not part of the car. How can the person become part of the car? WEAR SEATBELTS

Video Clips Play Newton’s 1st Law of Motion clip (2:13)
(United Streaming)

Newton’s Ideas Continued
Newton’s second law shows how force, mass, and acceleration link together. The 2nd law shows that both the size of the force and the mass of the object affect the object’s acceleration. Force is measured in a unit Newton (N).

2nd Law F = m x a

2nd Law F = Force m = Mass a = Acceleration

2nd Law (F = m x a) How much force is needed to accelerate a 1400 kilogram car 2 meters per second/ second? Write the formula F = m x a Fill in given numbers and units F = 1400 kg x 2 meters per second/second Solve for the unknown 2800 kg-meters/second/second or 2800 N

Newton’s Ideas Continued
Newton’s Third Law is often called the action-reaction in action law.

For every action, there is an equal and opposite reaction.
3rd Law For every action, there is an equal and opposite reaction.

Newton’s 3rd Law in Nature
Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).

3rd Law Flying gracefully through the air, birds depend on Newton’s third law of motion. As the bird pushes down on the air with their wings, the air pushes their wings up and gives them lift.

3rd Law The reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases. The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.

Review 3 Laws of Motion