Mass, weight and density Flashcards
Define mass and weight, also stating their SI units.
Mass is the measure of the amount of matter in a body. (SI unit: kg)
Weight is the measure of the amount of gravitational force acting on it. (SI unit: N)
Are both mass and weight always constant for the same object?
No. Mass is constant as the object has a constant amount of matter in it. However, weight is the force the gravitational field exerts on the object, so it depends on the gravitational field strength of the environment the object it is in.
What is the relationship between weight and mass?
W = mg
Weight = mass x gravitational field strength
What is a gravitational field?
It is a region in which a mass experiences a gravitational force due to gravitational attraction.
[When a mass is placed in a gravitational field, it experiences a gravitational force. The phrases ‘gravitational force’ and ‘weight’ can be used interchangeably.]
Define gravitational field strength.
It is the gravitational force acting per unit mass.
What is the gravitational field strength on Earth?
10N/kg or 10k^-1
[To be more accurate, 9.81, which is the value of acceleration during free-fall]
Define inertia.
Inertia refers to the reluctance of an object to change its state of motion due to its mass.
What is the relationship between inertia and mass?
The greater the mass of an object, the greater its inertia.
Define density.
Density of a substance is the mass per unit volume
What is the formula for density?
density = mass/volume
What is the density of water?
1g/cm^3 or 1000kg/m^3
How to measure the density of regular/irregular objects and liquids?
Use an electronic mass balance to measure the mass of the object/liquid.
mass=measured mass - mass of beaker
Regular: measure dimensions and calculate volume
Irregular: use displacement can to find volume
Liquid: use a measuring cylinder to find volume
Calculate density using the formula.
