Gravity and Motion

Who said the quote what goes up must come down?

Sir Isaac Newton

The question is… why?

Why do all objects fall

down?

The answer…

What happened in ancient Greece around 400 BCE?

Who questioned Aristotle idea?

When did it happen?

Gravity and Acceleration

The acceleration due to the gravity is the same for all objects. Why is this true?

A heavier object experiences a greater gravitational force than a lighter object does. But a heavier objects is also more difficult to accelerate because it has more mass, this produces a balance.

Acceleration due to GravityAll the objects accelerate

towards the Earth a rate of 9.8m/s/s.

So, for every second that an object falls, its velocity increases

in 9.8 m/s.

Downward!

MATH PROBLEMS

A boy standing on a high cliff dives into the ocean below and strikes the water after 3s. What is the boy’s velocity when he hits the water?

A foul ball is hit straight up in the air and falls from the top of its motion for 1.4s before being caught by the catcher. What is the velocity of the ball as it hits the catcher’s glove?

A brick falls from the top of a building and strikes the ground with a velocity of 19.6 m/s downward. How long does the brick fall?

= GravityThe first one, Gravity (or G Force), reigns supreme. Why, you ask?

It’s all about the range.

Yep, Gravity rules.

It’s also important for life. Without it, the Sun would be lonely—not attracted to the Earth at all!

Gravity is the real deal. So let’s explore this G-Force more!

The gravitational force (or Fg) between two objects depends on each object’s mass

The Force gets stronger as the total mass of the objects gets bigger.

Gravitational Force

Gravitational force is the attraction between all masses in the universe—like the attraction of the earth's mass to bodies (like ours) near its surface. And it looks like this:

The gravitation between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them.

In math lingo, you might say:

GravitationalForce universal

gravitational constant

masses of the two objects

distance between the two objects

But don’t worry, as Albert Einstein said:

Phew!

Gravitation cannot be held responsible for people falling in

love.

First Law of MotionNow we know that Gravity is a serious Force, but it can be confusing. That’s where our man Isaac Newton comes in to help with his First Law of Motion:

Objects at rest (or in motion) stay that way unless acted on by an outside Force.

Discussion Questions:

What is the object here?

Is it in motion or at rest?

And what is the Force that acts on the object?

Then comes Newton’s Second Law of Motion:

F=Ma Force equals Mass times acceleration.

In other words, Forces make mass move by accelerating it.

Discussion Questions:

What changed when the size of the soccer balls changed?

How did this change (from a small soccer ball to a gigantic one) affect the acceleration?

Why?

DESCRIBE THE FOLLOWING PICTUREWhat are the forces and motion applied? Explain