igcse-cambridge-combined-double-solution Archives - Fridge Physics

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Wave Speed

Wave speed is given in meters per second (the number of waves that pass per second). Wavelength is measured in meters and frequency is measured in hertz (Hz), or number of waves per second.

Demo

In this tutorial you will learn how to calculate the speed of a wave.

The equation for this calculation is written like this:

$v = { \text f \; \text x \; \lambda }$

Chilled practice question

Calculate the velocity of a wave with a wavelength of 6 m and a frequency of 50 Hz

Frozen practice question

Find the velocity of a wave which has a time period of 10 s and a wavelength of 24 m, you will need to calculate the frequency from the wave period equation first.

Science in context

Wave speed is given in meters per second (the number of waves that pass per second). Wave Speed = Frequency x Wave length. Wavelength is measured in meters and frequency is measured in hertz (Hz), or number of waves per second.

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Turning Moments

The size of the turning effect is called a turning moment. As Newton’s first law of motion states, an object will remain at rest if the forces are balanced. When the sum of the forces add to zero, a body will remain at rest or move at a constant velocity.

Demo

In this tutorial you will learn how to calculate the moments and apply the results to a real life situation for example forces acting on a see-saw.

The equation for this calculation is written like this:

$M = { \text F \; \text x \; \text D}$

Chilled practice question

The anticlockwise moment is is 75 Nm. What distance from the pivot must you place a 2.5 Kg mass for the clockwise and anticlockwise moments to equal ? Take gravity as 10N\Kg

Frozen practice question

You sit 2 m away from the pivot on a see-saw and your weight is 500 N. Your friend has a mass of 25 Kg. How far away from the pivot on the other side should they sit for the see-saw to balance ? Take gravity as 10N/Kg

Science in context

The size of the turning effect is called a turning moment.
Turning moment = force x perpendicular distance from the pivot.
As Newton’s first law of motion states, an object will remain at rest if the forces are balanced.
When the sum of the forces add to zero, a body will remain at rest or move at a constant velocity.

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Moments

Forces can cause an object to rotate and the turning effect of the force is called a moment. If a resultant force acts on an object about a fixed turning point called the pivot or fulcrum it will cause the object to rotate e.g. using a spanner, a screwdriver, opening a door hanging on hinges.

Demo

In this tutorial you will learn how to calculate the moment in a real life example.

The equation for this calculation is written like this:

$M = { \text F \; \text x \; \text D}$

Chilled practice question

A 5 N force is applied to a spanner 15 cm from the pivot. Calculate the moment.

Frozen practice question

A screwdriver was used to open a tin of paint with a moment of 1.5 Nm exerted 25 cm from the pivot. What force was being applied ?

Science in context

Forces can cause an object to rotate and the turning effect of the force is called a moment. If a resultant force acts on an object about a fixed turning point called the pivot or fulcrum it will cause the object to rotate e.g. using a spanner, a screwdriver, opening a door hanging on hinges. M = F x d, where M = the moment of a force (Nm), F = force applied (N) and d (m) is the distance from the pivot or fulcrum.

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Force on a Spring

When a force acts on a spring it is stretched or compressed, its length will changes by an amount e from its original length.

Demo

In this tutorial you will learn how to calculate the force on a spring given its extension and spring constant.

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

The equation for this calculation is written like this:

$F = { \text k \; \text x \; \text e}$

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.

A spring is stretched 0.25 m, it has a spring constant of 20 N/m, calculate the force on the spring.

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..

A force of 10 N is applied to a spring and it extends by 20 cm, calculate its spring constant.

Science in context

When a spring is stretched or compressed, its length will changes by an amount x from its original length,  force  F = ke. The force the spring exerts is its restoring force, it acts to restore the spring to its original length.

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Pressure

Pressure can be calculated if you know the force applied to or by an object and the contact area. The units are newtons per square meter, or N/m2.

Demo

In this tutorial you will learn how to calculate the pressure exerted by an object if you have been given the force applied to the object and given area.

The equation for this calculation is written like this:

$P = { \text F \; \text / \; \text A}$

Chilled practice question

The base of a brief case has an area of 25 cm 2 and a mass of 5 Kg. Calculate the pressure exerted by the briefcase when placed on a surface. Take the force of Gravity as 10N/Kg.

Frozen practice question

An elephant exerts a pressure of 53500 N/m2 one of its feet has an area of 0.15 m2. Calculate the mass of the elephant. Take the force of Gravity as 10N/Kg.

Science in context

Pressure can be calculated if you know the force applied and the area using the physics equation, P = F/A. Pressure is equal to force divided by area, units are newtons per square meter, or N/m2.

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Force, Mass and Acceleration

An object of constant mass accelerates in proportion to the force applied.

Demo

In this tutorial you will learn how to calculate the force applied to an object if you are given its mass and acceleration.

The equation for this calculation is written like this:

$F = { \text m\; \text x \; \text a}$

Chilled practice question

Calculate the force applied to cannon ball which accelerates at 7m/s2 which has a mass of 5 Kg.

Frozen practice question

A rocket has a driving force of 15 N and a mass of 250 g. Calculate the acceleration of the rocket.

Science in context

Force (N) = mass (kg) × acceleration (m/s²). Therefore, an object of constant mass accelerates in proportion to the force applied.

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Kinetic Energy

In physics, the kinetic energy (KE) of an object is the energy that it has due to its motion. It is defined as the work needed for an object of a known mass to accelerate to a given velocity.

What is Kinetic energy?

In physics, the kinetic energy (KE) of an object is the energy that it has due to its motion. It is defined as the work needed for an object of a known mass to accelerate to a given velocity.

Kinetic energy equation

To calculate Kinetic energy we write the equation like this.

$E_k = { 1 \over2} mv {^2}$

Kinetic energy demo

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

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.

Calculate the Kinetic energy store in a car with a mass of 850 Kg moving at a velocity of 3.5 m/s.

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.

A meteorite has 8000 J of Kinetic energy, calculate its mass if it has a velocity of 20 m/s

Science in context

Anything that is moving has energy in its kinetic energy store.

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Power

The quantity power is the rate at which work is done. The quicker work is done the greater the power.

What is Power?

The quantity power is the rate at which work is done. The quicker work is done the greater the power. The standard metric unit of power is the Watt. The calculation of power is the work done in Joules divided by a unit of time seconds. 1 Watt is equivalent to 1 joule of work done per second. Many machines have their power rating displayed upon them in Watts, the higher the value the greater the power of the machine and the faster the rate of energy transfer.

Power equation

To calculate Power we write the equation like this.

$P = { W \over \text{t}} = { E \over \text{t}}$

Power demo

In this tutorial you will learn how to calculate power, the rate of doing work during an energy transfer.

Chilled practice question

Calculate the power of an electric fire if it transfers 950 KJ of energy in 5 minutes 30 seconds.

Frozen practice question

An electric heater has a power rating of 2200 W. How long to the nearest second does it take to transfer 500 KJ of energy.

Science in context

Power is the rate of energy transfer per second.

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Charge

The size of the current is the rate of flow of charge. Electrons are negatively charged particles which transfer energy through wires as electricity.

What is Charge?

The size of the current is the rate of flow of charge. Electrons are negatively charged particles which transfer energy through wires as electricity. Charge is measured in coulombs (C). Electrons are really small and the effect of one electron would be really difficult to measure, It is easier to measure the effect of a large number of electrons. One Coulomb of charge contains 6 Ã— 1018 electrons.

Charge equation

To calculate Charge we use this equation.

$Q = { \mathit I \, \mathit t} $

Charge demo

In this tutorial you will learn how to calculate the the charge flowing in an electrical circuit.

Chilled practice question

Calculate the charge when a current of 16 A flows for 2 minutes.

Frozen practice question

How long must a current of 26 A flow to transfer 936 KC.

Science in context

The size of the current is the rate of flow of charge.

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Resistance

Resistance is an electrical quantity that measures how a device or material reduces the electrical current flow through it.

What is Resistance?

Resistance is an electrical quantity that measures how the device or material reduces the electrical current flow through it. Resistance is measured in ohms (Ω).If we make a comparison of resistance to water flow in pipes, the resistance is greater when the pipe is thinner, so the water flow is decreased It slows down which also happens to the flow of electricity.

Resistance equation

To calculate Resistance we write the equation like this.

$V = { \mathit I \, \mathit R} $

Resistance demo

In this tutorial you will learn how to calculate the resistance in an electrical circuit.

Chilled practice question

Calculate the resistance of a bulb supplied with 8 V and a current flow of 2 A.

Frozen practice question

Calculate the current in a circuit which has a resistance of 16 Ω and a potential difference of 8 V.

Science in context

Resistance reduces the flow of electricity.

Millie’s Master Methods

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