Mass, Weight and

Gravity

Student Learning Objectives

Students will be able to explain mass of objects with reference to a basic atomic structureStudents will be able to differentiate between mass and weightStudents will be able to calculate weight using the formula

Force = mass x acceleration due to gravityStudents will use the computational tool, Microsoft Excel, to solve for weights on different planets and graphically analyze the effects of gravity on weight

Obviously, it’s the ……

Help the kids with their discussion.

Which will get to the ground first in free fall, the elephant or the feather?

Free fall means air does not affect the feather

What is free fall?

WHAT IS GRAVITY ? • A force of attraction between any two masses

• It is not only an attraction between an object and the earth

• It is an attraction between all masses in the universe

GRAVITY• The more mass an object

has the more gravitational force.

• The sun’s gravity keeps the

earth in its orbit

• The Moon's gravity pulls on the Earth and makes the tides rise and fall every day

• Masses on the earth accelerate due to the force of gravity

• Who knows the acceleration due to gravity on the earth?http://phet.colorado.edu/en/simulation/gravity-and-orbits

MASS• The amount of matter or “stuff” an object contains

• This matter or “stuff” is atoms, the small particles everything in the universe is made of

• Atoms contain: Nucleus – Protons and Neutrons Electrons

MASS• What is the unit of

measurement of mass?

• The more matter an object contains the greater its mass

• An object’s mass stays the same wherever it is

WEIGHT• The force on the object due to gravity

• Weight is a force• Force = Mass x Acceleration due to gravity

• Weight changes based on acceleration due to gravity

• The unit of weight is Newton (N), named after the scientist Isaac Newton

http://www.youtube.com/watch?v=SegMt7sa42E

Materials List: pencil, netbook,  Tommy has a weight of 294 N on earth. Find Tommy’s weight (force) on the moon, and the other planets.

ACTIVITY 2 – Weight on Planets

294 ???

294 ???

Mass = Force ÷ acceleration due to gravity = ÷ = kg

 Force = mass x acceleration due to gravity = X = N

  

Find Tommy’s weight on the other planets

We must first find Tommy’s mass because it will stay the same everywhere

ACTIVITY 2 – Weight on Planets

A greater acceleration due to gravity cause a greater weight.

A smaller acceleration due to gravity cause a smaller weight.

Conclusion

294 ???

If all objects have the same acceleration on earth, once there is no resistance from air they will fall at the same rate.

Conclusion