Topic 3 Flashcards
What is mass?
Mass is defined as a measure of the quantity of matter in an object at rest relative to the observer.
What property does mass represent?
Mass is the property of an object that resists change in motion.
How does mass affect motion?
The greater the mass of an object, the more difficult it is to speed it up, slow it down, or change its direction.
Is mass a scalar or vector quantity?
Mass is a scalar quantity that has magnitude but no direction.
What is the unit of mass?
Mass is measured in kilograms (kg).
How can mass be converted from grams to kilograms?
To convert grams (g) to kilograms (kg), divide the mass in grams by 1000.
How can mass be converted from kilograms to grams?
To convert kilograms (kg) to grams (g), multiply the mass in kilograms by 1000.
What is weight?
Weight is a gravitational force on an object with mass.
Is weight a scalar or vector quantity?
Weight is a vector quantity with both magnitude and direction.
What is the unit of weight?
Weight is measured in newtons (N).
What is the relationship between weight and gravitational field strength?
Weight is the effect of a gravitational field on a mass.
What defines gravitational field strength?
Gravitational field strength is defined as the force per unit mass acting on an object in a gravitational field.
What is the gravitational field strength on Earth?
On Earth, gravitational field strength is equal to 9.8 N/kg.
What is the formula for gravitational field strength?
g = W/m, where g is gravitational field strength, W is force of weight, and m is mass of object.
What is the acceleration of free fall on Earth?
In a uniform gravitational field, an object in free fall accelerates at a rate of 9.8 m/s².
How does mass differ from weight?
An object’s mass always remains the same, regardless of its location in the Universe.
How does weight change with location?
The weight force exerted on an object will differ depending on the strength of the gravitational field in its location.
What is the gravitational field strength on the Moon?
The gravitational field strength on the Moon is 1.63 N/kg.
How does weight compare on the Moon versus Earth?
An object’s weight will be about 6 times less on the Moon than on Earth.
What is density?
Density is defined as the mass per unit volume of a material.
What is the equation for density?
The equation for density is ρ = m / V.
What do the symbols in the density equation represent?
ρ = density (kg/m³), m = mass (kg), V = volume (m³).
How can you use a formula triangle for density?
To use a formula triangle, cover up the quantity you wish to calculate to reveal the structure of the equation.
How does density relate to mass and volume?
Objects made from low density materials typically have a low mass, while similarly sized objects made from high density materials have a high mass.
Give an example comparing densities.
A bag full of feathers is lighter than the same bag full of metal.
Another example is that a balloon is less dense than a small bar of lead despite occupying a larger volume.
Why are gases generally less dense than solids?
Gases are generally less dense than solids because the particles in a gas are more spread out.
How does the density of a gas compare to its liquid or solid form?
A gas is less dense than the same substance in liquid or solid form.
What units are used for density?
If mass is in grams and volume in cm³, density is in g/cm³. If mass is in kg and volume in m³, density is in kg/m³.
How can you determine the volume of an object?
The volume may not always be given directly but can be calculated with the appropriate equation depending on the object’s shape.
What is the density of a paving slab with a mass of 73 kg and dimensions 0.04 m × 0.5 m × 0.85 m?
The density is 4300 kg/m³.
Calculation steps: Volume = 0.04 m × 0.5 m × 0.85 m = 0.017 m³; ρ = 73 kg / 0.017 m³.
What is an important tip for converting units?
When converting a larger unit to a smaller one, multiply; when converting a smaller unit to a larger one, divide.
Convert 125 m to cm.
125 m = 12,500 cm.
Convert 5 g to kg.
5 g = 0.005 kg.
What is the aim of Experiment 1?
The aim of this experiment is to determine the densities of regular objects by using measurements of their dimensions.
What is the independent variable in Experiment 1?
Type of shape / volume.
What is the dependent variable in Experiment 1?
Mass of the object.
What equipment is needed for Experiment 1?
Digital balance, ruler, Vernier callipers, or micrometer.
What is the method for measuring the density of regularly shaped objects?
Place the object on a digital balance, measure its dimensions, repeat measurements, and calculate the density.
How should results be recorded in Experiment 1?
A suitable results table must contain space for multiple readings and any calculations that need to be performed.
What formula is used to calculate density in Experiment 1?
Density = Mass / Volume.
What is the aim of Experiment 2?
This experiment aims to determine the densities of irregular objects using a displacement technique.
What is the independent variable in Experiment 2?
Different irregular shapes / mass.
What is the dependent variable in Experiment 2?
Volume of displaced water.
What equipment is needed for Experiment 2?
Eureka can and measuring cylinder.
What is the method for measuring the density of irregularly shaped objects?
Place the object on a digital balance, fill the eureka can with water, lower the object into the can, and measure the displaced water volume.
How should results be recorded in Experiment 2?
A suitable results table must contain space for multiple readings and any calculations that need to be performed.
What is the relationship between the volume of displaced water and the object?
The volume of the water displaced is equal to the volume of the object.
What is the aim of Experiment 3?
This experiment aims to determine the density of a liquid by finding a difference in its mass.
What is the independent variable in Experiment 3?
Volume of water added.
What is the dependent variable in Experiment 3?
Mass of cylinder.
What equipment is needed for Experiment 3?
Measuring cylinder.
What is the method for measuring the density of liquids?
Place an empty measuring cylinder on a digital balance, fill it with liquid, and note the mass and volume.
How should results be recorded in Experiment 3?
A suitable results table must contain space for multiple readings and any calculations that need to be performed.
How is the mass of the liquid calculated in Experiment 3?
Mass of liquid = Mass of cylinder with liquid – mass of cylinder.
What are systematic errors in the experiments?
Ensure the digital balance is set to zero before taking measurements.
What are random errors in the experiments?
Errors in measurements of length; take repeat readings and calculate an average.
What safety considerations should be taken during the experiments?
Handle glassware carefully, do not pour water into the measuring cylinder on the balance, and stand during the experiment.
What determines whether an object floats or sinks?
Whether an object floats or sinks depends on the relative densities of the object and the fluid it is submerged in.
What happens if an object is denser than the fluid?
If the object is denser than the fluid, it will sink.
What happens if an object is less dense than the fluid?
If the object is less dense than the fluid, it will float.
What is upthrust?
Upthrust is a force that pushes upwards on an object submerged in a fluid.
In which direction does upthrust act in relation to weight force?
Upthrust always acts in the opposite direction to the object’s weight force.
What factors affect the size of the upthrust force?
The size of the upthrust force depends on the density of the fluid and the volume of fluid that is displaced.
How does the density of a liquid affect upthrust?
The denser the liquid, the greater the force of upthrust exerted on the object.
When will an object float?
An object will float if the force of upthrust is equal to the force of weight.
What happens if the force of upthrust is less than the object’s weight?
If the force of upthrust on an object is less than the object’s weight, then the object will sink.
What happens if the density of the object is greater than the density of the fluid?
If the density of the object is greater than the density of the fluid, then the object will sink.
What happens if the density of the object is less than the density of the fluid?
If the density of the object is less than the density of the fluid, then the object will float.
What is an example of an object that floats in water?
A polystyrene block will float in water.
This is because polystyrene has a density of 0.05 g/cm³ which is much less than the density of water (1.0 g/cm³).
What is an example of an object that partially submerges but still floats?
A wooden block will be partially submerged but will still float.
This is because the density of a wooden block (0.9 g/cm³) is slightly less than the density of water.
What is an example of an object that sinks in water?
An iron block will sink.
This is because iron has a density (7.9 g/cm³) that is much higher than water.
What density must a mineral oil have for potassium to sink in it?
For potassium to sink, the density of the oil must be less than the density of the potassium (0.862 g/cm³).
Which mineral oil should a teacher choose to store potassium?
The teacher should choose liquid paraffin, which has a density of 0.825 g/cm³.
This is because it is less dense than potassium.
What is the main thing to remember about density?
The main thing to remember is that density is mass per unit volume.
In what units is mass usually measured in Physics?
In Physics, mass is almost always measured in kg.
What is true about lower density liquids and higher density liquids?
A liquid with a lower density will float on a liquid with a higher density if the liquids do not mix.
