Chapter 3 Density
The mass of an object can be measured with a
balance
Whether a hot-air balloon rises or falls, it can be controlled
by changing the density of the air inside the balloon.
As we climb up, atmospheric pressure
decreases
Pressure increases within
depth
If the buoyant force on an object is less than the object's weight, the net force on the object is
downward and the object will accelerate downward.
If the buoyant force due to air pressure on an object is large enough, the object can
float in air.
When a balloon is filled with helium, it is less dense than the air around it, and so the balloon
floats
The volume of a liquid can be measured with a
graduated cylinder
A gas can exert pressure on an object. That pressure depends on the
height of the gas above the object.
State the formula for Density.
D= M/V Density is equal to the mass divided by the volume.
What are types of fluids? Can fluids exert force?
Liquids and gases. Yes
What is a fluid?
A fluid is a material that can flow and has no definite shape.
What does a hydrometer do?
A hydrometer is an instrument that measures the density of a fluid.
What is a rectangular solid?
A six-faced block in which all faces are rectangular.
What is buoyant force?
Buoyant force is the net upward force exerted on an object in a fluid by the surrounding fluid.
Is Density a physical property? Why?
Density is a physical property because that means we can measure it without changing the composition of the material whose density is being measured.
What is Density?
Density is the amount of mass per unit volume of a material.
Does the size of the buoyant force depend on depth?
NO
State the formula for pressure?
P= F/A Pressure is equal to the force divided by the surface area.
What is the SI unit of pressure
Pascal, abbreviated Pa.
How can we find the volume of an object with an irregular shape?
Place it in a liquid and measure the volume of liquid the object displaces. We can calculate its density by dividing its mass by its volume
What does pressure depend on?
Pressure depends on the area over which a force is exerted and the size of the force.
What is pressure?
Pressure is the force per unit area applied on the surface of an object
State Archimedes' principle
The buoyant force on an object is equal to the weight of the fluid the object displaces.
What is atmospheric pressure?
The force exerted per unit area by air particles.
State the formula for the volume of a rectangular solid
V= l x w x h Volume is equal to the length times the width times the height.
What does Density depend on?
What the object is made of, the mass of the particles that make up the material, and the distance between the particles in the material.
Helium gas is less dense than nitrogen gas and oxygen gas, which are the main components of
air
An object will float if it is
less dense than the fluid around it.
