ocr-physics-b21c-paper-2 Archives - Fridge Physics

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Pressure in a Gas

Gas Pressure is created when gas particles collide with the walls of their container. The more often the particles collide with the walls, and the faster they are moving, the greater the pressure.

Demo

In this tutorial you will learn how to calculate the gas pressure in enclosed spaces depending on the containers volume.

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:

$pV = { \text K}$

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 gas in a sealed container has a volume of 12 m3. The pressure of the gas is 80 Pa. The volume of the container is increased and the pressure falls to 60 Pa. What is the new volume of the container ? The temperature of the gas remains unchanged.

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.

The volume of a gas is reduced from 10 m3 to 2.5 m3 . The original pressure is 200 Pa. Calculate the new pressure.

Science in context

Pressure in a gas is caused when gas particles collide with the walls of their container. The more often the particles collide with the walls, and the faster they are moving when they do this, the greater the pressure. This is why the pressure in a tyre goes up when more air is pumped in.

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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.

Millie’s Master Methods

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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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Specific Heat Capacity

Specific heat capacity is how much heat energy is required to raise 1 kg of a substance by 1 °C.

What is Specific heat capacity?

Specific heat capacity is how much heat energy is required to raise 1 kg of a substance by 1 °C. Specific heat capacity is the amount of heat energy required to raise the temperature of a substance per unit of mass. The specific heat capacity of a material is a physical property and different materials have a different specific heat capacities.

Specific heat capacity equation

To calculate Specific heat capacity we write the equation like this.

$\Delta E = mc\Delta\theta$

Specific heat capacity demo

In this tutorial you will learn how to calculate how much energy is required to raise the temperature of a known mass of a substance.

Chilled practice question

The specific heat capacity of water is 4200 J/Kg/ °C. Calculate the energy needed to raise 4 Kg of water from 18 °C to 35 °C.

Frozen practice question

Calculate the S.H.C of 750 g of material which needs 14 KJ of heat energy to raise its temperature by 22 °C ?

Science in context

Specific heat capacity is how much heat energy is required to raise 1 kg of a substance by 1 °C.

Millie’s Master Methods

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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.

Millie’s Master Methods

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Elastic Potential Energy

Stretching or squashing an object can transfer energy into its elastic potential energy store.

What is Elastic potential energy?

Stretching or squashing an object can transfer energy into its elastic potential energy store. Elastic energy is the mechanical potential energy stored in the material. Elastic energy occurs when objects are compressed, stretched or deformed.

Elastic potential energy equation

To calculate Elastic potential energy we use this equation.

$E_e = { 1 \over2} ke {^2}$

Elastic potential energy demo

In this tutorial you will learn how to calculate the energy stored in a stretched spring.

Chilled practice question

A spring is stretched 200 cm. The spring has a spring constant of 30 N/M. Calculate the stored elastic potential energy of the stretched spring.

Frozen practice question

Calculate the extension of a spring if it has a stored elastic potential energy of 540 J and a spring constant of 30 N/M.

Science in context

Stretching or squashing an object can transfer energy into its elastic potential energy store.

Millie’s Master Methods

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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 × 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.

Millie’s Master Methods

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