Chapter 23 Section 3

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Chapter 23 Section 3 NEWTON’S SECOND LAW OF MOTION

Use the power point, the exercises done during the lessons and the lab reports to study for the test

Newton’s Second Law of Motion * “The force of any object is the product of its mass times its acceleration” *This law explains how the force of an object changes according to its mass and its acceleration

“The force of any object is the product of its mass times its acceleration” There is a formula that describes this law: F = m X a ( Unit is N – Newton)

With this formula you can calculate: Force of an object F = m X a Acceleration of an object a = F/m Mass of an object m = F/a

F=mxa According to the formula: A) what does force depends on? Mass and acceleration

B) what is the relationship between force and mass????? (if the mass is bigger the force necessary to change the motion of an object will be bigger)

The unit for force: Newton 1 Newton = 1kg X m/s2

To calculate Force : F=mXa Force is in N = kg X m/s2 Acceleration (a) is in m/s2 Mass has to be in Kg

1 g = 1000 Kg

grams to Kg = divide by 1000

Example F= m x a Mass = 40 gr Acceleration = 9.8 m/s2 Change 40 gr into Kg = 0.04 kg

F = 0.04 X 9.8 = 0.39 N

Galileo Experiment - handout Galileo Galilei - Lived in Italy, in the 16th century in a city called Pisa According to GG if you go on top of the Pisa Tower and drop two similar objects with different masses, they will hit the ground at the same time.

Gravity *”A force that attracts two objects towards each other” It depends on the mass of the objects and the distance between the two objects.

The closer they are the stronger is the pull The bigger the objects the stronger is the pull.

Gravity 1) why is that we do not fell the pull of the objects around us? 2) why do we fall to the ground? Why is that the center of the Earth can exert such a strong pull on our bodies? 1) Because the objects are too small to exert a significant pull. 2) Because the Earth is really big compared to us.

The acceleration of Gravity: Objects in free fall are subject to gravity, also called gravitational acceleration of gravity. This force equals 9.8 m/s2 This force is the same for all objects in free fall, no matter how big they are.

Air Resistance – type of friction Friction it is a force that resists the motion of two surfaces rubbing against each other. Air resistance happens because the molecules of air will collide with any object in motion, slowing down this object.

The two balls used during our experiment, have different surfaces, so the friction acting on both balls is different and this can explain why they do not fall at exactly the same speed.

Resistance depends on the shape and type of surface A pointy object will suffer less air resistance than the other two objects.

There is less surface in contact with the air.

Explain why the moon and the Earth will never collide. There are 2 forces acting on the moon. What are these forces?????

Explain why the moon and the Earth will never collide.

Explain why the moon and the Earth will never collide. Earth is bigger than the moon = there is a force that pulls the moon towards the Earth which is gravity

Moon has a straight motion and tends to continue moving straight due to INERTIA the two forces will combine “forcing” the moon to move on an elliptical orbit around the Earth.