Chapter 2: The Laws of Motion

What do you think? Agree or Disagree?

Lesson 1: Gravity and Friction

A push or pull on an object.

Described by:

A force gives an object energy to:

Force

•STRENGTH•DIRECTION

•STOP MOVING•START MOVING•CHANGE DIRECTION

Contact Force

Non Contact Force

Types of Force

Contact and Noncontact Sports

How do these relate to the title of this lesson? (Gravity and Friction?)

Contact = frictionNoncontact = gravity

Contact Noncontact

A push or pull on one object by another that is touching it.

Contact Force

Contact forces can be: Strong OR Weak

A force that one object can apply to another object without touching it.

Noncontact Force

Examples Include:

Gravity Magnetic Force Electric Force

can be used to show forces.

The of an arrow shows the

of the force.

The that the arrow points shows the direction in which the

The stronger the force the the arrow.

Strength and Direction of Forces

ARROWS

DIRECTION

LENGTHSTRENGTH

FORCE WAS APPLIED

LONGER

The SI unit for force is the

The symbol for Newton is

One Newton = about the force you exert to lift a lime.

Named after:

Strength and Direction of Forces

NEWTON

N

Sir Isaac Newton (founder of physics)

An attractive force that exists between all objects that have mass.

Gravity

Force of gravity On EARTH the force of gravity = 9.8 m/s2

All objects fall to the Earth at an acceleration of 9.8m/s2 due to the force of gravity.

Sir Isaac Newton (1600’s)

The law states:

Factors Affecting Gravity

The Law of Universal Gravitation

•MASS•DISTANCE

All objects are attracted to each other by a gravitational force. The strength of force depends on the MASS of each object and the DISTANCE between them.

The amount of matter in an object.Mass

Which object has more mass?

When the mass of one or both objects the gravitational force between them also

Regardless of the amount of mass an object has the will be the

Each object exerts the attraction on the other object.

Gravitational Force and MASS

INCREASES

INCREASES

FORCE ARROWS

SAME SIZE

SAME

The attraction between objects as the between the object

Gravitational force and DISTANCE

DECREASES

DISTANCE INCREASES

The gravitational force exerted on an object.

Weight is measured in

Near Earth’s surface the object’s weight is the

Weight

NEWTONS

FORCE DUE TO GRAVITY

Weight and mass are related, but ARE NOT the same.

Weight can due to

Mass change

FORCE =

Weight and Mass on Earth

CHANGE GRAVITY

DOES NOT

MASS x ACCELERATION

F =

Weight on Earth =

M x A

MASS x 9.8m/s2 (acceleration due to the force of gravity)

What would an object with a mass of 10 kg weigh?

If your mass was 50kg, what would your weight be?

Examples:

The combination of all the forces acting on an object.

To calculate the net force:

◦ If the forces act in the same direction they are added together.

◦ If forces act in opposite directions they are subtracted.

Net Force

Forces acting on an object that combine and form a net force that is not zero.

Unbalanced forces cause an object to move. Forces moving in the same direction are

Forces moving in the opposite direction are

Combining Forces - Unbalanced

ADDED

SUBTRACTED

Forces acting on an object that combine and form a net force of ZERO. NO change in motion.

Combining Forces – Balanced Forces

A force that resists the motion of two surfaces that are touching.

Types of friction

Friction

•STATIC FRICTION

•SLIDING FRICTION

•FLUID FRICTION

Friction that acts on objects thatare not moving.

Static Friction

When solid objects slide over each other.

Sliding Friction

A force produced by a fluid (gases or liquids) Examples: engine oil, grease

Air resistance

Air resistance is affected by:

*objects with more surface area have more air resistance**

Fluid Friction

•SHAPE•SIZE•MASS

•a type of fluid friction•Upward force exerted on falling objects.

2 causes of friction When microscopic dips and bumps that cover

surfaces slide past another surface with dips and bumps they catch on to one another.

When a positive charge slides by a negative charge attraction occurs.

What causes friction?