Newton's Law of Gravitation

Here's a great video to help you really understand this law. Khan Academy is the best!

Also, here's a quiz I made about this law to help anyone about to take a test on it study.

True or False

a.     Newton’s Third Law states every action has an equal and similar reaction.

b.     If the two objects have the same mass, then they have the same acceleration.

c.     For every one object, there is a gravitational force.

d.     GC is the symbol used for the gravitational constant.

Short Answer

a.     What are the three items the force of gravity depends on?

b.     Write out the two equations used to find force.

c.     When is the tide high? Low? Explain your reasoning.

Answers

1.     False: equal and OPPOSITE 

2.     True

3.     False: for every TWO objects

4.     False: G is the gravitational constant

5.     Mass of each object, distance between the two objects (radius), gravitational constant

6.     Fg=G m1m2/r(squared) and F=ma

7.     High= when moon is on that side of Earth; Low= when moon is not on that side of Earth; This is because the Moon has a gravitational attraction to the Earth, just like Earth has a gravitational attraction to the Moon.

Newton's Second and Third Laws

Here is a summary of the notes I took on Newton's 2nd and 3rd Laws.

Newton’s 2^nd Law

·      A=f/m

·      Relationship that shows force is prop. to acceleration and mass is inversely prop. to acceleration

·      Inversely proportional: if mass increased by 2, acceleration would DECREASE by 2

·      Proportional: if force is increased two times greater, acceleration also increases 2 times more

Examples of 2^nd Law

·      A ball hitting a wall and bouncing back

·      A hammer striking a nail into a piece of wood and the hammer ”bounces” back

·      This picture shows how acceleration and mass are inversely proportional, but force and acceleration are proportional

Newton’s 3^rd Law

·      The force from the 1^st object to the 2^nd object is ALWAYS equal to the force from the 2^nd object to the 1^st object

·      Even if only one object is pulling, force is still equal

·      Dealing with two objects, not just one

·      Forces are separate for each object

Examples of 3^rd Law

·      A person standing on a skateboard, pushes on a wall, and accelerates backwards.

                              

o   The wall is applying a force to you causing you to move backwards

o   The person accelerates because only one force is acting on the person

o   The force of the person pushing the was and the table pushing back are independent of one another

·      This picture shows how a rocket is launched into space using Newton’s 3^rd Law

Review Questions to Remember

·      When skydiving, at what point is the net force…

o   0N?

§  When diving at a constant speed; terminal velocity

o   -_N?

§  When free falling; before reaching terminal velocity

o   +_N?

§  When the parachute has deployed

·      When skydiving, why is acceleration positive when parachute is deployed?

o   To slow down, accel. must be in opposite direction of velocity, and velocity is negative when skydiving, so accel. is positive

·      If an astronaut is traveling alone in space and needs to get back in the shuttle, how can he do this?

o   Push off of (or throw) tools he has with him in opposite direction of where he needs to go

Newton's First Law

In class today, we went over Newton's First Law. Here's my graphic organizer to give a better idea of this topic.