- Mass is the measure of the amount of substance in a body.
- Unit of mass: kilogram (kg), gram (g)
- Scalar quantity
- Measured using a beam balance
- Fixed value
- Inertia is directly proportional to mass. Inertia is the object’s reluctance to start/stop moving.
Volume
- Volume is amount of space the object occupies.
- The volume of the solid/liquid can be obtained using a measuring cylinder
- The volume of a regularly shaped solid or an irregularly shaped solid which sinks in water can be determined using displacement method.
Gravitational field
- Gravitational field is a region in which a mass experiences a force due to gravitational attraction.
- The strength of the gravitational field is due to the mass of the planet
- Gravitational field strength, g, measures the strength of the gravitational field
- Unit of gravitational field strength: Nkg-1
- g = 10 Nkg-1 at the surface of the Earth
- The strength of the gravitational field decreases as we get further away from the planet
Weight
- Weight is the gravitational force on the body.
- Units: Newton (N)
- Vector quantity. Points downward.
- Measured using a spring balance
- Weight = mass × gravitational field strength
- Weight depends on the distance of the object from the planet
Density
- Density is mass per unit volume
- Units of density: kgm-3, gcm-3 (1000kgm-3 = 1gcm-3)
- density = mass/volume.
- Scalar quantity
- Depends on type of material. Objects of different sizes made up of the same material will have the same density.
- The density of object can be obtained by measuring both the mass (beam balance) and volume of the object (displacement method). Then, use the equation (density = mass/volume)
- Average density = total mass/total volume
- Generally, heating causes an increase in volume without an increase in the mass. Density decreases. (Convection)
- If the object has a higher density than the surrounding medium, the object will sink. If the object has a lower density than the surrounding medium, the object will float. If the object has the same density as the surrounding medium, the object will suspend in the medium
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