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# March 26, 2014 Homework: Read pgs. 48-50, define highlighted terms from reading and pick two main ideas from each heading- leave spaces for additional.

## Presentation on theme: "March 26, 2014 Homework: Read pgs. 48-50, define highlighted terms from reading and pick two main ideas from each heading- leave spaces for additional."— Presentation transcript:

March 26, 2014 Homework: Read pgs , define highlighted terms from reading and pick two main ideas from each heading- leave spaces for additional notes (on pg. 7 in N.B)… Do Now: Write down homework: Open notebooks to pg. 5 and open textbooks to pg. 46.

Universal Gravitation
-Acts everywhere in the universe, not just on Earth. - Law of Universal Gravitation: the force of gravity acts between all objects in the universe. Any two objects in the universe, without exception, attract each other. You are attracted to the Earth and the Earth is attracted to you

Factors Affecting Gravity:
Mass and distance are the two factors that affect gravitational attraction between two objects. Mass is the measure of the amount of matter in an object. SI unit : kilograms (kg) Mass and gravitational force: the more mass an object has, the greater its gravitational force. If mass increases, the force of gravity increases Ex: the sun’s mass is so great it exerts a large gravitational force on the planets.

Distance between objects:
The farther apart two objects are the less gravitational force there is between them. If the distance between two objects increases, the force of gravity decreases

Weight and Mass Weight is the measure of gravitational force on an object -the force of gravity on a person or object at the surface of a planet It varies with the strength of gravitational force, mass does not. Gravity pulls on mass. Your mass in kilograms (kg) multiplied by the force of gravity (9.8 m/s²) = your weight. (1 kg= 2.2 lbs)

-What forces are acting on a sky diver, as they fall from the sky?
Write a question you have about the forces that act on a falling object? --Could there be anymore than what you have written?

What type of friction is this an example of?
Is the object moving? NO What type of friction is this an example of? -Static What would you have to do to break the force of static friction? Apply enough force to break static friction- which would turn into sliding friction

-What is the difference between mass and weight?
-What happens to the force of gravity between two objects when the distance decreases? -What is the difference between mass and weight? -Why do you weigh less on the moon than you do on Earth?

March 27, 2014 Homework: Section Assessment Questions: 2C, 3A, and 3B- on pg. 10 in your notebook Do Now: Write down homework, Update T.O.C- pg8: Gravity and Motion Pg. 9: Air Resistance activity Open notebook to page 7-

~~~Gravity and Motion~~~
Gravity, the downward force that affects all objects, and air resistance, fluid friction, both affect motion. **When you hold something then let go… Gravity becomes the unbalanced force that causes the object to fall Is the ball falling faster when it leaves your hand or when it is just about to hit the ground?

Gravity Causes Acceleration
Acceleration means speeding up, slowing down, or changing direction. Gravity Causes: --objects to accelerate; --an objects velocity (speed) to increase, when it has been dropped from any height --an object to change direction, when it is thrown horizontally

Projectile Motion Projectile: An object that is thrown
Gravity acts the same on objects moving horizontally as it does for objects moving vertically. -Gravity eventually pulls horizontally moving objects downward, at the same rate as objects dropping vertically

Which hits First?- activity
Besides gravity, what force acts on falling objects? Air resistance Why did it take the flat piece of notebook paper longer to reach the ground? Because it has a larger surface area, so the force of air resistance is greater.

Air Resistance- Air resistance is a type of fluid friction- that acts on a solid object moving through the air and in opposite direction of motion.- It is an upward force exerted on falling objects Not the same for all objects Falling objects with a greater surface area will have more air resistance. ex: a leaf falls more slowly than an acorn

What if there was not any Air resistance?
Because all objects freefall at the same rate 9.8 m/s²- no matter what their masses are. When dropped, two objects with different masses would hit the ground at the same time.

Free Fall An object is in free fall when the only force acting on it is gravity. When in free fall the object is accelerating---Why? Because the force of gravity is an unbalanced force, which causes the object to accelerate -All objects accelerate, because of gravity at a rate of 9.8 m/s---no matter what their masses are.

Terminal Velocity The greatest velocity a falling object reaches- when the force of air resistance equals the weight of the object. Air resistance increases with Velocity A falling object will eventually fall fast enough that the upward force- air resistance and downward force –gravity become equal. (**REMEMBER**)When forces are balanced no acceleration the velocity (speed) remains constant (even).

Projectile Motion Projectile: An object that is thrown
Gravity acts the same on objects moving horizontally as it does for objects moving vertically. -Gravity eventually pulls horizontally moving objects downward, at the same rate as objects dropping vertically

-What forces are acting on a sky diver, as they fall from the sky?
What does the skydiver experience during his fall to the Earth?

March 28, 2014 Homework: Read pgs : Review notes: and begin Force packet- pages 1-4 due for check in on Tuesday Do Now: Write down homework, put force packet away, Open notebooks to page. 10 Today I will… create a diagram that demonstrates why objects accelerate during free fall… Identify Newton’s 3 Laws of motion

March 28, 2014 Homework: Read pgs : Review notes: and begin Force packet- pages 1-4 due for check in on Tuesday Do Now: Write down homework, put force packet away, Open notebooks to page. 7/ 8 Today I will… create a diagram that demonstrates why objects accelerate during free fall Identify Newton’s 3 Laws of motion

Air Resistance- Air resistance is a type of fluid friction- that acts on a solid object moving through the air and in opposite direction of motion.- It is an upward force exerted on falling objects Not the same for all objects Falling objects with a greater surface area will have more air resistance. ex: a leaf falls more slowly than an acorn

What if there was not any Air resistance?
When dropped, two objects with different masses would hit the ground at the same time. Because all objects freefall at the same rate 9.8 m/s²- no matter what their masses are.

Free Fall An object is in free fall when the only force acting on it is gravity. When in free fall the object is accelerating---Why? Because the force of gravity is an unbalanced force, which causes the object to accelerate -All objects accelerate, because of gravity at a rate of 9.8 m/s---no matter what their masses are.

Terminal Velocity The greatest velocity a falling object reaches- when the force of air resistance equals the weight of the object. Air resistance increases with Velocity A falling object will eventually fall fast enough that the upward force- air resistance and downward force –gravity become equal. (**REMEMBER**)When forces are balanced no acceleration the velocity (speed) remains constant (even).

2C: How would your weight change on the surface of an Earth- Sized Planet whose mass was greater than Earth’s? Why? Your weight would be greater because the gravitational force is greater 3A.Why does an object accelerate when it falls toward the Earth’s surface? Gravitational force causes the object to accelerate toward the Earth 3B: How does the mass of an object affect its acceleration during free fall? An objects mass has no effect on its acceleration during free fall.

http://www. youtube. com/watch
and Gravity & Friction school house rock

-What forces are acting on a sky diver, as they fall from the sky?
What does the skydiver experience during his fall to the Earth?

Newton’s Big 3 Newton’s Three Law’s of Motion:
1st: Law of Inertia, objects at rest will stay at rest, objects in motion will stay in motion 2nd: The force needed to move an object is equal to the product of that objects mass and Acceleration; F= m x a 3rd: For every action there is an equal and opposite reaction.

Newton’s 1st Law 1st: (Law of Inertia) Objects that are at rest, stay at rest. Objects that are in motion will stay in motion at constant velocity (speed) unless an unbalanced force acts on it, which accelerates the object. Inertia: the tendency to keep moving. It depends on the mass of the object. The more mass an object has the more inertia..

Newton’s 2nd Law 2nd: The force needed to move an object is equal to the product of that objects mass and Acceleration; F= m x a

Newton’s 3rd Law 3rd: For every action there is an equal and opposite reactions

Projectile motion How does gravity affect objects that are moving horizontally?

Is the ball falling faster when it leaves your hand or when it is just
Highlights! Is the ball falling faster when it leaves your hand or when it is just about to hit the ground? -When you throw a baseball, how can you tell that the force of gravity is acting on it? The ball eventually falls to the ground It falls faster when it hits the ground

What happens to the force of gravity between two objects when the distance decreases?
What is the difference between mass and weight? -Why do you weigh less on the moon than you do on Earth?

1) Is the object moving? 2)What type of friction is this an example of? 3) What is the Net force of these forces? 4) What would you have to do to break this force of friction?

Label all the forces acting on the sky diver as she falls toward the Earth’s surface-
-Draw the arrows to show strength and direction of the forces and what forces those arrows represent. 2) Write if the forces are balanced or unbalanced and if unbalanced in what direction is the net force acting? *Note:*Assume that picture B. is when terminal velocity has occurred. 3) For picture C. What force changes when a sky diver’s parachute opens? What forces stay the same?

Negative direction of the net force
Force can be in the negative direction when pointing to the left or downwards.

Fig. 3 in book>

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