PHYSICS PAPER 2 (KEY CONCEPTS CAN ALSO COME) 8.5 Describe how to measure the work done by a force and
TOPIC 8 – ENERGY – FORCES DOING WORK understand that energy transferred (joule, J) is equal to work done
8.1 Describe the changes involved in the way energy is stored when (joule, J)
systems change - To make an object move, some force needs to act on it. This force
- A SYSTEM is a single/group of objects (it is anything you define it to needs a source of energy (food/duel). The force causes energy to be
be). When a system CHANGES, the way energy is stored changes; transferred from the energy store of the force to the object's energy
energy is transferred. This is because energy is never created or store. Thus, whenever a force acts on an object through a distance,
destroyed. It is only ever transferred between stores energy is transferred. This is ‘WORK DONE’.
- Thus, when a system changes, energy is either transferred between - Thus: ‘ENERGY TRANSFERRED’ is the same as ‘WORK DONE’
objects, or between stores. - When a force moves an object through a distance, WORK IS DONE
8.2 Draw and interpret diagrams to represent energy transfers and ENERGY IS TRANSFERRED
Energy transfers can be shown using a Sankey diagram or energy flow - WORK DONE & ENERGY TRANSFERRED is measured in joules, J
diagrams 8.6 Recall and use the equation: work done (joule, J) = force
8.3 Explain that where there are energy transfers in a closed system (newton, N) × distance moved in the direction of the force (metre,
there is no net change to the total energy in that system m) E = F × d
- In a CLOSED SYSTEM, energy cannot escape. Any energy transfers FORMULA for WORK DONE: E = F × d
will have no net change in the TOTAL energy of that system
8.4 Identify the different ways that the energy of a system can be 8.7
changed: a) through work done by forces Describe and calculate the changes in energy involved when a
b) in electrical equipment c) in heating system is changed by work done by forces
Energy in a system can be transferred through 3 ways:
1) WORK DONE BY FORCES: When a force moves an object over a
distance. EG: lifting a box
2) BY ELECTRICAL EQUIPMENT: When current flows through a 8.8 Recall and use the equation to calculate the change in
component. EG: electric toothbrush/hair dryer gravitational PE when an object is raised above the ground: change
3) BY HEATING: Energy transferred from hotter objects to colder ones. in gravitational potential energy (joule, J) = mass (kilogram, kg) ×
EG: Heating a pan of water gravitational field strength (newton per kilogram, N/kg) × change in
vertical height (metre, m) ∆GPE = m× g ×∆h
,GRAVITATIONAL POTENTIAL ENERGY: An energy store in an object due 8.12 Define power as the rate at which energy is transferred and
to its position at any height above the earth’s surface. This is due to the use examples to explain this definition
force of gravity pulling it down. Measured in JOULES. FORMULA: - POWER is the RATE OF ENERGY TRANSFER. Basically, power is how
much work is being done (energy transferred) every second
- The unit of power is watt (W). 1W = 1 J/s
m – mass (kg) h – CHANGE in vertical height - The larger the power of an object, the more work it does per second.
g – gravitational field strength (N/kg) [a measure of the strength of For example, if an electric heater has a power of 600 W , it means it
gravity, changes in different planets, given in question. EARTH: 9.8/10] transfers 600J of energy every second. A 1200 W heater would transfer
twice as much energy per second, thus would heat a room quicker.
8.9 Recall and use the equation to calculate the amounts of energy
8.13 Recall and use the equation: power (watt, W) = work done
associated with a moving object: kinetic energy (joule, J) = 2 1 ×
(joule, J) ÷ time taken (second, s) P = E/T
mass (kilogram, kg) × (speed)2 ((metre/second)2, (m/s)2) 2 2 1 KE = ×
m× v FORMULA for POWER: P = E/T
KINETIC ENERGY: Energy stored in moving objects. (stationary objects
have no kinetic energy). Measured in JOULES (j [kj is 1000 joules])
8.14 Recall that one watt is equal to one joule per second, J/s
8.15 Recall and use the equation for efficiency:
8.10
Explain, using examples, how in all system changes energy is
dissipated so that it is stored in less useful ways
8.11 Explain that mechanical processes become wasteful when
they cause a rise in temperature so dissipating energy in heating
the surroundings
- No device is 100% efficient, energy is always dissipated
- If a mechanical process causes a rise in temperature, energy is
dissipated, heating the environment. This energy is WASTED.
EG: In a washing machine, energy is used to rotate the drum. However,
as it spins, some energy is wasted as sound & heat.
, TOPIC 9 – FORCES AND THEIR EFFECT 9.3 Use vector diagrams to illustrate resolution of forces, a net
9.1 Describe, with examples, how objects can interact force, and equilibrium situations (scale drawings only)
a) at a distance without contact, linking these to the gravitational, - VECTOR DIAGRAMS use arrows to scale that show the direction &
electrostatic and magnetic fields involved magnitude of the forces acting on an object. These can illustrate:
b) by contact, including normal contact force and friction 1) RESOLUTION OF FORCES: This is when you split a vector acting at
c) producing pairs of forces which can be represented as vectors an angle into its horizontal & vertical components.
- A force is a push/pull on an object caused by it interacting with - This can be done by drawing the vector to scale, then add the
something. This ‘interaction’ can be of 2 types: horizontal & vertical components along the gridline & measure them
a) CONTACT: These are forces that require the objects involved to be 2) NET FORCE: When a number of forces are acting on an object, these
touching. For example, the NORMAL CONTACT FORCE when 2 objects can be replaced by a single force that has the same effect as all the
interact & FRICTION. original forces together. This is called the RESULTANT FORCE (NET
b) NON-CONTACT: These are forces that can act between objects that FORCE).
aren’t touching. For example, GRAVITATIONAL ATTRACTION (caused - If all the forces are PARALLEL then to find the resultant force add the
by gravitational fields), ELECTROSTATIC (attraction/ repulsion between forces going in the same direction & subtract any going in the opposite
electric charges) & MAGENTIC FIELDS. direction
- Whenever 2 objects interact (by contact OR non-contact force) both - If the forces are acting at an angle, the resultant force can be found by
objects feel an EQUAL & OPPOSITE force (Newtons 3 rd law). This using vector diagrams. The steps are:
creates a pair of forces which can be represented as VECTORS 1) Find a suitable scale (eg 5N = 1cm) & draw all forces acting on the
(arrows) in a diagram object ‘tip-to-tail’
9.2 Explain the difference between vector and scalar quantities 2) Then draw a straight line from the start of the first force, to the end
using examples of the last force. This line shows the direction & magnitude of the
All quantities are of two types: resultant force (net force).
1) SCALAR: They have a magnitude (size) but NO direction
EG: speed, distance, mass, energy, temperature, time
2) VECTOR: They have a magnitude (size) AND direction
EG: force, velocity, displacement, weight, acceleration, momentum
TOPIC 8 – ENERGY – FORCES DOING WORK understand that energy transferred (joule, J) is equal to work done
8.1 Describe the changes involved in the way energy is stored when (joule, J)
systems change - To make an object move, some force needs to act on it. This force
- A SYSTEM is a single/group of objects (it is anything you define it to needs a source of energy (food/duel). The force causes energy to be
be). When a system CHANGES, the way energy is stored changes; transferred from the energy store of the force to the object's energy
energy is transferred. This is because energy is never created or store. Thus, whenever a force acts on an object through a distance,
destroyed. It is only ever transferred between stores energy is transferred. This is ‘WORK DONE’.
- Thus, when a system changes, energy is either transferred between - Thus: ‘ENERGY TRANSFERRED’ is the same as ‘WORK DONE’
objects, or between stores. - When a force moves an object through a distance, WORK IS DONE
8.2 Draw and interpret diagrams to represent energy transfers and ENERGY IS TRANSFERRED
Energy transfers can be shown using a Sankey diagram or energy flow - WORK DONE & ENERGY TRANSFERRED is measured in joules, J
diagrams 8.6 Recall and use the equation: work done (joule, J) = force
8.3 Explain that where there are energy transfers in a closed system (newton, N) × distance moved in the direction of the force (metre,
there is no net change to the total energy in that system m) E = F × d
- In a CLOSED SYSTEM, energy cannot escape. Any energy transfers FORMULA for WORK DONE: E = F × d
will have no net change in the TOTAL energy of that system
8.4 Identify the different ways that the energy of a system can be 8.7
changed: a) through work done by forces Describe and calculate the changes in energy involved when a
b) in electrical equipment c) in heating system is changed by work done by forces
Energy in a system can be transferred through 3 ways:
1) WORK DONE BY FORCES: When a force moves an object over a
distance. EG: lifting a box
2) BY ELECTRICAL EQUIPMENT: When current flows through a 8.8 Recall and use the equation to calculate the change in
component. EG: electric toothbrush/hair dryer gravitational PE when an object is raised above the ground: change
3) BY HEATING: Energy transferred from hotter objects to colder ones. in gravitational potential energy (joule, J) = mass (kilogram, kg) ×
EG: Heating a pan of water gravitational field strength (newton per kilogram, N/kg) × change in
vertical height (metre, m) ∆GPE = m× g ×∆h
,GRAVITATIONAL POTENTIAL ENERGY: An energy store in an object due 8.12 Define power as the rate at which energy is transferred and
to its position at any height above the earth’s surface. This is due to the use examples to explain this definition
force of gravity pulling it down. Measured in JOULES. FORMULA: - POWER is the RATE OF ENERGY TRANSFER. Basically, power is how
much work is being done (energy transferred) every second
- The unit of power is watt (W). 1W = 1 J/s
m – mass (kg) h – CHANGE in vertical height - The larger the power of an object, the more work it does per second.
g – gravitational field strength (N/kg) [a measure of the strength of For example, if an electric heater has a power of 600 W , it means it
gravity, changes in different planets, given in question. EARTH: 9.8/10] transfers 600J of energy every second. A 1200 W heater would transfer
twice as much energy per second, thus would heat a room quicker.
8.9 Recall and use the equation to calculate the amounts of energy
8.13 Recall and use the equation: power (watt, W) = work done
associated with a moving object: kinetic energy (joule, J) = 2 1 ×
(joule, J) ÷ time taken (second, s) P = E/T
mass (kilogram, kg) × (speed)2 ((metre/second)2, (m/s)2) 2 2 1 KE = ×
m× v FORMULA for POWER: P = E/T
KINETIC ENERGY: Energy stored in moving objects. (stationary objects
have no kinetic energy). Measured in JOULES (j [kj is 1000 joules])
8.14 Recall that one watt is equal to one joule per second, J/s
8.15 Recall and use the equation for efficiency:
8.10
Explain, using examples, how in all system changes energy is
dissipated so that it is stored in less useful ways
8.11 Explain that mechanical processes become wasteful when
they cause a rise in temperature so dissipating energy in heating
the surroundings
- No device is 100% efficient, energy is always dissipated
- If a mechanical process causes a rise in temperature, energy is
dissipated, heating the environment. This energy is WASTED.
EG: In a washing machine, energy is used to rotate the drum. However,
as it spins, some energy is wasted as sound & heat.
, TOPIC 9 – FORCES AND THEIR EFFECT 9.3 Use vector diagrams to illustrate resolution of forces, a net
9.1 Describe, with examples, how objects can interact force, and equilibrium situations (scale drawings only)
a) at a distance without contact, linking these to the gravitational, - VECTOR DIAGRAMS use arrows to scale that show the direction &
electrostatic and magnetic fields involved magnitude of the forces acting on an object. These can illustrate:
b) by contact, including normal contact force and friction 1) RESOLUTION OF FORCES: This is when you split a vector acting at
c) producing pairs of forces which can be represented as vectors an angle into its horizontal & vertical components.
- A force is a push/pull on an object caused by it interacting with - This can be done by drawing the vector to scale, then add the
something. This ‘interaction’ can be of 2 types: horizontal & vertical components along the gridline & measure them
a) CONTACT: These are forces that require the objects involved to be 2) NET FORCE: When a number of forces are acting on an object, these
touching. For example, the NORMAL CONTACT FORCE when 2 objects can be replaced by a single force that has the same effect as all the
interact & FRICTION. original forces together. This is called the RESULTANT FORCE (NET
b) NON-CONTACT: These are forces that can act between objects that FORCE).
aren’t touching. For example, GRAVITATIONAL ATTRACTION (caused - If all the forces are PARALLEL then to find the resultant force add the
by gravitational fields), ELECTROSTATIC (attraction/ repulsion between forces going in the same direction & subtract any going in the opposite
electric charges) & MAGENTIC FIELDS. direction
- Whenever 2 objects interact (by contact OR non-contact force) both - If the forces are acting at an angle, the resultant force can be found by
objects feel an EQUAL & OPPOSITE force (Newtons 3 rd law). This using vector diagrams. The steps are:
creates a pair of forces which can be represented as VECTORS 1) Find a suitable scale (eg 5N = 1cm) & draw all forces acting on the
(arrows) in a diagram object ‘tip-to-tail’
9.2 Explain the difference between vector and scalar quantities 2) Then draw a straight line from the start of the first force, to the end
using examples of the last force. This line shows the direction & magnitude of the
All quantities are of two types: resultant force (net force).
1) SCALAR: They have a magnitude (size) but NO direction
EG: speed, distance, mass, energy, temperature, time
2) VECTOR: They have a magnitude (size) AND direction
EG: force, velocity, displacement, weight, acceleration, momentum
