Understanding Weight and Mass: A Comparison and Their Relationship with Gravity, Study notes of Physics

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W H I C H O N E D E P E N D S O N T H E O T H E R?

Weight and Mass

(or is it Mass and Weight?)

True or False

1. The force of gravity is the same for all objects on earth.
2. Gravity is caused by the rotation of the earth.
3. There is no gravity on the moon.
4. A chicken in a vacuum experiences no gravity.
5. You exert as large a gravitational force on the earth as it exerts on you.

Weight = mass x g

 The weight of an object is directly proportional to its mass, as shown by the equation weight=9.8(mass).  This means if an object’s mass is tripled, its weight triples, and if its mass is halved, its weight is also halved.  For example, a 4 kg watermelon would weigh 39.2 N, which is four times the 9.8N that a 1kg mango would weigh.

What is weight?

 The size of the gravitational force on a body, exerted by Earth (or the chunk or matter body is on).  NOT 9.8 for all objects  NOT the same for all objects  The magnitude of the gravitational force  Units: N (newton)  F g =9.8m or Fg = mg (g = accel. due to gravity)  Measured with a spring scale

What is mass?

 The measure of an object’s resistance to acceleration (inertia)  One of the two properties of all matter  A SCALAR  Measured in kg in the SI system  NOT the force of gravity  NOT weight  Measured by trying to accelerate object

Mass is a fundamental property of matter, there is no formula to define it. A measure of the amount of inertia (resistance to acceleration) for an object. Mass is one way to measure how much of something you have. SI unit: kg (kilogram) alternate units: gram, slug 1.0 liter of water has a mass of 1.0kg Mass does NOT change for an object, regardless of where it is in the universe, unless the amount of matter changes

m: mass

(scalar)