Mass, Weight and Gravity

Which will get to the ground first in free fall, the elephant or the feather? Free fall means air does not affect the feather Obviously, it’s the …… Free fall: A situation where the only force acting on the body is due to it’s weight. What is free fall?

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 . As the Moon passes over the ocean, there is a swell in the sea level. 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? G or kg 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 measure of the gravitational pull between two objects. A spring scale (e.g., the typical bathroom scale), balance scale compares masses; it will read the same on the moon. The force on the object due to gravity 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

ACTIVITY 2 – Weight on Planets Tommy has a weight of 294 N on earth. Find Tommy’s weight (force) on the moon, and the other planets. ??? 294

ACTIVITY 2 – Weight on Planets What is the moons gravity? ACTIVITY 2 – Weight on Planets 294 ??? We must first find Tommy’s mass because it will stay the same everywhere Mass = Force ÷ acceleration due to gravity Fweight = m x a Begin by dividing each side by a (acceleration), getting m (mass) alone a a Multiply Tommy’s mass by the acceleration due to gravity on the moon or plant

Conclusion A greater acceleration due to gravity results in a greater weight. A smaller acceleration due to gravity results in a smaller weight. If all objects have the same acceleration on earth, once there is no resistance from air they will fall at the same rate. ??? 294