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Density

Density is a measure of how compact the particles are in a substance. Density is defined as the mass per unit volume.

What is Density

Density is a measure of how compact the particles are in a substance. Density is defined as the mass per unit volume. It is mathematically defined as mass divided by volume: ρ = m/V. The density(ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) Of the substance.

Density equation

To calculate Density we use this equation.

${\rho} = {\text{m} \over\text{V}}$

Density demo

In this tutorial you will learn how to calculate the density of different substances.

Chilled practice question

A block has a mass of 20 Kg and a volume of 0.25 m3. Calculate its density.

Frozen practice question

A barrel has a mass of 2500 g and a density of 2 Kg/m3. Calculate the barrels volume.

Science in context

Density is a measure of how compact the particles are in a substance.

Millie’s Master Methods

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Specific Latent Heat

Specific latent heat is the energy needed to change the state of a substance.

What is Specific latent heat?

Specific latent heat is the energy needed to change the state of a substance. Latent heat is the energy absorbed or released by a substance during a change in its physical state. The latent heat is normally shown as the amount of heat energy in joules per Kg mass of the substance undergoing the change of state.

Specific latent heat equation

To calculate Specific latent heat we use this equation.

$E = {\text{m} \text{L}}$

Specific latent heat demo

In this tutorial you will learn how to calculate the energy needed for different substances to change their state of matter.

Chilled practice question

The specific latent heat of water for melting is 334000 J/Kg. How much heat energy needed to melt a 30 Kg block of ice ?

Frozen practice question

What is the specific latent heat of a material if 2 Kg of the material releases 95.5 KJ of energy when it melts ?

Science in context

Specific latent heat is the energy needed to change the state of matter a substance.

Millie’s Master Methods

The Fridge Physics Store

Energy Transformed

The potential difference between two points is the energy transferred per unit charge. An electrical circuit is an energy transformation device.

What is Energy transformed?

The potential difference between two points is the energy transferred per unit charge. An electrical circuit is an energy transformation device. Energy is provided to the circuit by an electrochemical cell, battery, generator or another electrical energy source. Energy is delivered by the circuit. The rate at which this energy transformation takes place has a great relevance to the design of an electrical circuit for useful functions.

Energy transformed equation

To calculate Energy transformed we use this equation.

Energy = power x time

$ {\mathit E \, \text = \mathit P \mathit t}$

Energy = charge flow x potential difference

$ {\mathit E \, \text = \mathit Q \mathit V}$

Energy transformed demo

In this tutorial you will learn how to calculate the energy transformed through an electrical circuit.

Chilled practice question

Calculate the energy transformed if a circuit is supplied with 6 V and 32 C of charge flows.

Frozen practice question

Calculate the energy transformed when a current of 4 A flows with a p.d of 230 V for 18 s.

Science in context

The potential difference between two points is the energy transferred per unit charge

Millie’s Master Methods

The Fridge Physics Store

Forces and Work Done

The unit for work done is the joule (J), or Newton meter (N-m). One joule is equal to the amount of work that is done when 1 N of force moves an object over a distance of 1 m.

Demo

In this tutorial you will learn how to calculate the work done to move an object through a known distance.

Note-Some mobile devices may require you to tap full screen during playback to view video content.

The formula for this equation is written like this:

w = f x d

Chilled practice question

Copy out the question and attempt to calculate the answer before watching the solution. Write down the equation and show all of your working, remember to add the units to your answer, this routine will guarantee you maximum marks in an exam. Mark your solution and correct if needed.

How much work has been done if a car is pushed along the road 550 cm with a force of 400 N ?

Frozen practice question

Copy out the question and attempt to calculate the answer before watching the solution. Write down the equation and show all of your working, remember to add the units to your answer, this routine will guarantee you maximum marks in an exam. Mark your solution and correct if needed.

75 J of work is done pulling a trolley 150 cm. Calculate the force applied.

Science in context

Work can be calculated with the equation: Work = Force × Distance. The unit for work is the joule (J), or Newton • meter (N • m). One joule is equal to the amount of work that is done when 1 N of force moves an object over a distance of 1 m.

Millie’s Master Methods

The Fridge Physics Store

Momentum

All moving objects have momentum. Forces can cause changes in momentum. The total momentum in a collision or explosion is conserved and stays the same. Car safety features absorb energy involved in a crash they slow down the collision thus reducing the force of impact.

Demo

In this tutorial you will learn how to calculate the momentum in a moving object.

The equation is written like this:

$P = { \text m\; \text x \; \text v}$

Chilled practice question

Calculate the momentum of a 1200 Kg vehicle travelling at 5 m/s.

Frozen practice question

A girl has a mass of 60 Kg. How fast is she moving if her momentum is 240 Kgm/s ?

Science in context

All moving objects have momentum. Forces can cause changes in momentum. The total momentum in a collision or explosion is conserved and stays the same. Car safety features absorb energy involved in a crash they slow down the collision thus reducing the force of impact.

Millie’s Master Methods

The Fridge Physics Store

Transformers

A transformer is an piece of electrical apparatus which will increase or decrease the voltage in an alternating current. It can be designed to “step up” or “step down” voltages and is based on the magnetic induction principle.

Demo

In this tutorial you will learn how to calculate voltages in step up and step down transformers.

The equation is written like this:

${ \text V_{1} \; \text / \; \text V_{2} \; \text = \; \text N_{1} \; \text / \; \text N_{2} \;}$

Chilled practice question

A transformer has 300 turns on its primary coil and 100 turns on it secondary coil. What voltage is induced in the secondary coil if the primary voltage is 96 V ?

Frozen practice question

A transformer has 320 turns on the primary coil and 800 turns on the secondary coil. Find the voltage across the primary coil when the voltage across the secondary coil is 1320 V.

Science in context

A transformer is an piece of electrical apparatus which will increase or decrease the voltage in an alternating current. It can be designed to “step up” or “step down” voltages and is based on the magnetic induction principle.When a voltage is introduced to one coil, called the primary coil it magnetizes its core which is made from iron which induces a voltage in the secondary coil.

Millie’s Master Methods

The Fridge Physics Store

The Motor Effect

A current-carrying wire or coil can exert a force on a permanent magnet. The force increases if the strength of the magnetic field and/or current increases. This is called the motor effect.

Demo

In this tutorial you will learn how to calculate the force on a wire carrying a current in a magnetic field.

The equation is written like this:

$F = { \text B \; \text x \; \text I \; \text x \; \text L}$

Chilled practice question

Calculate the force on a wire carrying a current of 3 A. 0.25 m of the wire is in the magnetic field. The magnetic flux density is 15 T.

Frozen practice question

The force on a wire in a magnetic field is 30 N. The magnetic flux density is 3 T and the length of wire in the magnetic field is 50 cm. Calculate the current.

Science in context

A current-carrying wire or coil can exert a force on a permanent magnet.The force increases if the strength of the magnetic field and/or current increases. This is called the motor effect.

Millie’s Master Methods

The Fridge Physics Store

Uniform Acceleration

Uniform or constant acceleration is a type of motion in which the velocity of an object changes by an equal amount in every equal time period.

Demo

In this tutorial you will learn how to calculate uniform acceleration.

The equation is written like this:

${ \text v^{2} \; \text – \; \text u^{2} \; \text = \; \text 2as}$

Chilled practice question

A racing car travelling at 20 m/s decelerates uniformly at 1.5 m/s2 towards a slip road 100 m away. Calculate its velocity when it reaches the slip road.

Frozen practice question

A ball is dropped 12 m from the top of a building. Calculate the velocity of the ball when it hits the ground. Ignore any value for air resistance. Acceleration due to gravity is 9.8m/s2

Science in context

Uniform or constant acceleration is a type of motion in which the velocity of an object changes by an equal amount in every equal time period.

Millie’s Master Methods

The Fridge Physics Store

Pressure in Fluids

Fluid pressure is exerted on the surface of an object in a liquid. This pressure causes upthrust . An object placed in a liquid will begin to sink. As it sinks, the liquid pressure on it increases and so the upthrust increases.

Demo

In this tutorial you will learn how to calculate the pressure on an object in a fluid at a known depth.

The equation is written like this:

$P = { \text h \; \text x \; \text p \; \text x \; \text g}$

Chilled practice question

Calculate the pressure 180 m below the surface of sea water. The density of sea water is 1025 Kg/m3. Use Gravity as 9.8 N/kg.

Frozen practice question

Calculate the density of a liquid if the pressure exerted is 5880 Pa at a depth of 75 cm, take the Gravitational field strength of the Earth to be 9.8 N/Kg.

Science in context

Fluid pressure is exerted on the surface of an object in a liquid. This pressure causes upthrust. An object placed in a liquid will begin to sink. As it sinks, the liquid pressure on it increases and so the upthrust increases.

Millie’s Master Methods

The Fridge Physics Store

Acceleration

Acceleration is how quickly the velocity is changing whether it be speed, direction or both. Acceleration is a measure of how quickly the velocity of an object is changing.

Demo

In this tutorial you will learn how to calculate the acceleration of a moving object.

The equation is written like this:

$a = { v \unicode{x2013} u \over \text{t}}$

Chilled practice question

Calculate the acceleration if the velocity increases from 4 m/s to 76 m/s in 8 s.

Frozen practice question

How long does it take for the velocity of a bus to increase from 12 m/s to 20 m/s if it is accelerating at 4 m/s2.

Science in context

Acceleration is how quickly the velocity is changing whether it be speed, direction or both.

Millie’s Master Methods

The Fridge Physics Store

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