OCR physics B21C – P2
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.…
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…
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…
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.
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.
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…
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…
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…
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.
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.
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.
The power of an appliance is the energy that is transferred per second. Electric power is the rate, per unit time at which electrical energy is transferred by an electric circuit. What is Electrical power? The power of an appliance is the energy that is transferred per second. Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The unit for power is the watt, which is the transfer of energy at the rate of one joule per second. Electric power can be produced by electric generators and batteries. Electrical power equation To calculate Electrical power we use this equation. $ {\mathit P \, \text = \mathit V \mathit I}$ Electrical power demo In this tutorial you will learn how to calculate the electrical power of an electrical appliance. Chilled practice question Calculate the power in a circuit when a p.d of 18 V and a current of 4 A is measured. Frozen practice question Find the current flowing through an appliance which has a power rating of 14 KW and a p.d of 230 V. Science in context The power of an appliance is the energy that is transferred per second
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.
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.
The radioactivity of a sample decreases over time. Half life is a measurement of this decrease. What is Half life? The radioactivity of a sample decreases over time. Half life is a measurement in this decrease.The half-life of a radioactive substance is a constant for each radioactive material. It measures the time it takes for a known amount of the substance to become reduced by half due to radioactive decay, and therefore, the emission of radiation. Half life demo In this tutorial you will learn how to calculate the half life of a radioactive material. Chilled practice question The activity of a radio-isotope is 1536 cpm. What is its activity after five half lives? Frozen practice question A radio-isotopes activity falls from 1880 cpm to 235 cpm in 72 minutes. Calculate it’s half life. Science in context The radioactivity of a sample decreases over time. Half life is a measurement of this decrease
Lifting an object in a gravitational field transfers energy into the objects gravitational energy store. Gravitational potential energy is the energy an object has due to its height above Earth. What is Gravitational potential energy? Lifting an object in a gravitational field transfers energy into the objects gravitational energy store. Gravitational potential energy is the energy an object has due to its height above Earth. The equation for gravitational potential energy is GPE = mgh, where m is the mass in kilograms, g is the gravitational field strength (9.8 N/Kg on Earth), and h is the height above the ground in meters. Gravitational potential energy equation To calculate Gravitational potential energy we use this equation. $E_p = mgh$ Gravitational potential energy demo In this tutorial you will learn how to calculate the energy stored in an elevated 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. A barrel is lifted onto a shelf 3.5 m from the ground. The barrel has a mass of 22 Kg.…
The efficiency of a device is the proportion of input energy that is converted to useful energy. What is Efficiency? The efficiency of a device is the proportion of input energy that is converted to useful energy. Efficiency is a measure of how much work or energy is conserved in an energy transfer, work or energy can be lost, for example as wasted heat energy. The efficiency is the useful energy output, divided by the total energy input, and can be given as a decimal always less than 1 or a percentage. No machine is 100% efficient. Efficiency equation To calculate Efficiency we use this equation. $efficiency = {\text{useful energy output} \over\text{total energy input}}$ Efficiency demo In this tutorial you will learn how to calculate how efficient a device is at transferring energy from one form to another. Chilled practice question Calculate the efficiency of a light bulb with a total input energy of 500 J. The bulb emits 200 J of light energy and 300 J of heat energy. Frozen practice question A tumble drier is 80% efficient. Its useful energy is 45 KJ what is the total input energy in Joules. Science in context The efficiency of a device is the proportion of…
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…
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.…
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.
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…
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.
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.
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.
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.
Speed is how fast an object is moving in no given direction. Velocity is how fast an object is moving in a given direction. In physics, you can calculate the average speed by taking the total distance travelled and dividing it by the total time required to travel that distance. Demo In this tutorial you will learn how to calculate the speed of an object, velocity is speed with direction for example 20 m/s north. The equation is written like this: $S = { \text D / T}$ Chilled practice question Calculate the speed of a car which travels 2000 m in 400 s. Frozen practice question How long does it take a car to travel 360 m at 12 m/s ? Science in context Speed is how fast an object is moving in no given direction. Velocity is how fast an object is moving in a given direction.
Weight is the force acting on an object due to gravity. The weight of an object is defined as the force of gravity on the object and can be calculated as the mass times the acceleration due to gravity. Demo In this tutorial you will learn how to calculate the weight of an object on the moon due to its force of gravity. The equation is written like this: ${ \textit W} = {\text m \;} {\text x \;} {\text g}$ 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 weight of a flag pole on the moon, it has a mass of 5 Kg. 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.…
Weight is the force acting on an object due to gravity. The weight of an object can be defined as the force of gravity on the object. Since the weight is a force, its unit is the Newton. Demo In this tutorial you will learn how to calculate the weight of an object due to the force of the Earths gravity. The equation is written like this: ${ \textit W} = {\text m \;} {\text x \;} {\text g}$ Chilled practice question Calculate the weight of a bench on Earth which has a mass of 25 Kg. Frozen practice question Calculate the mass of an elephant if it has a weight of 60 KN on Earth. Science in context Weight is the force acting on an object due to gravity.
