mass, weight
October 27, 2016
Warm Up
What is Newton's 1st law?
Objectives: ­ be able to describe the difference between mass and weight
­be able to use an equation to relate gravitational force and mass
­be able to calculate the gravitational force between any 2 objects
CCSS:
­Question and seek answers.
­Identify significance and meaning.
­Understand relevance to surrounding world.
­Demonstrate learning through project­based activity.
­Collaborate to find solutions and to create meaning.
mass, weight
October 27, 2016
­ be able to describe the difference between mass and weight
Mass vs. Weight
Mass and weight are not the same thing.
­ be able to describe the difference between mass and weight
Mass (___): the amount of matter in an object.
Units:
Mass does not change from location to location!
If your mass was 80 kg...
m = 80 kg
m = 80 kg
moon
m = 80 kg
earth
Jupiter
mass, weight
October 27, 2016
­ be able to describe the difference between mass and weight
Weight (____): the amount that gravity pulls on an object.
Weight does change with location!
Units: "Weight" is also called " gravitational force"
If your mass was 80 kg...
Fg = 128 N
Fg = 784 N
moon
2
g = 1.6 m/s
Fg = 2000 N
earth
2
g = 9.8 m/s
Jupiter
2
g = 25 m/s
­be able to use an equation to relate gravitational force and mass
Equation that relates mass and weight:
Fg = mg
(This equation is only good near the surface
of a planet or other celestial body.)
mass, weight
October 27, 2016
­be able to use an equation to relate gravitational force and mass
A cat has a mass of 7 kg. What is the weight of the cat?
If the same cat is measured to have a weight of 60 N on Planet X, what is the gravitational acceleration of this planet?
­be able to calculate the gravitational force between any 2 objects
Universal Gravitation
This equation is good for any two objects with mass.
-11
G = 6.67 x 10 ______
Fg = Gm1m2
2
r
m1,m2 = masses of 2 objects
r = distance measured from
CENTERS of 2 objects
What are the units for G
that will make this
equation valid?
mass, weight
October 27, 2016
­be able to calculate the gravitational force between any 2 objects
Calculate the force of gravity between _______ and _______. (Assume _______'s mass is around 50 kg and _______'s mass is around 55 kg.)
­be able to calculate the gravitational force between any 2 objects
2
How we get g = 9.8 m/s (calculationally...)
mass, weight
October 27, 2016
­ be able to describe the difference between mass and weight
­be able to use an equation to relate gravitational force and mass
­be able to calculate the gravitational force between any 2 o
bjects
Homework
Can do #1­17
Gravitational forces of planets worksheet