Mechanics

1 Motion, forces and energy

1.1 Physical quantities and measurement techniques

 1 Describe the use of rulers and measuring cylinders to find a length or a volume

 2 Describe how to measure a variety of time intervals using clocks and digital timers

 3 Determine an average value for a small distance and for a short interval of time by measuring multiples (including the period of oscillation of a pendulum)

 4 Understand that a scalar quantity has magnitude (size) only and that a vector quantity has magnitude and direction

 5 Know that the following quantities are scalars: distance, speed, time, mass, energy and temperature

 6 Know that the following quantities are vectors: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength

 7 Determine, by calculation or graphically, the resultant of two vectors at right angles, limited to forces or velocities only

1.2 Motion

 1 Define speed as distance travelled per unit time; recall and use the equation v = s/t

 2 Define velocity as speed in a given direction

 3 Recall and use the equation average speed = total distance travelled/ total time taken

 4 Sketch, plot and interpret distance–time and speed–time graphs

 5 Determine, qualitatively, from given data or the shape of a distance–time graph or speed–time graph when an object is:

 (a) at rest

 (b) moving with constant speed

 (c) accelerating

 (d) decelerating

 6 Calculate speed from the gradient of a straight- line section of a distance–time graph

 7 Calculate the area under a speed–time graph to determine the distance travelled for motion with constant speed or constant acceleration

 8 State that the acceleration of free fall g for an object near to the surface of the Earth is approximately constant and is approximately 9.8 m/s^2

 9 Define acceleration as change in velocity per unit time; recall and use the equation a = v/t

 10 Determine from given data or the shape of a speed–time graph when an object is moving with:

 (a) constant acceleration

 (b) changing acceleration

 11 Calculate acceleration from the gradient of a speed–time graph

 12 Know that a deceleration is a negative acceleration and use this in calculations

 13 Describe the motion of objects falling in a uniform gravitational field with and without air/ liquid resistance (including reference to terminal velocity)

1.3 Mass and weight

 1 State that mass is a measure of the quantity of matter in an object at rest relative to the observer

 2 State that weight is a gravitational force on an object that has mass

 3 Define gravitational field strength as force per unit mass; recall and use the equation g = W/ m and know that this is equivalent to the acceleration of free fall

 4 Know that weights (and masses) may be compared using a balance

 5 Describe, and use the concept of, weight as the effect of a gravitational field on a mass

1.4 Density

 1 Define density as mass per unit volume; recall and use the equation ρ = m/V

 2 Describe how to determine the density of a liquid, of a regularly shaped solid and of an irregularly shaped solid which sinks in a liquid (volume by displacement), including appropriate calculations

 3 Determine whether an object floats based on density data

 4 Determine whether one liquid will float on another liquid based on density data given that the liquids do not mix

1.5 Forces

1.5.1 Effects of forces

 1 Know that forces may produce changes in the size and shape of an object

 2 Sketch, plot and interpret load–extension graphs for an elastic solid and describe the associated experimental procedures

 3 Determine the resultant of two or more forces acting along the same straight line

 4 Know that an object either remains at rest or continues in a straight line at constant speed unless acted on by a resultant force

 5 State that a resultant force may change the velocity of an object by changing its direction of motion or its speed

 6 Describe solid friction as the force between two surfaces that may impede motion and produce heating

 7 Know that friction (drag) acts on an object moving through a liquid

 8 Know that friction (drag) acts on an object moving through a gas (e.g. air resistance)

 9 Define the spring constant as force per unit extension; recall and use the equation k = F/x

 10 Define and use the term ‘limit of proportionality’ for a load–extension graph and identify this point on the graph (an understanding of the elastic limit is not required)

 11 Recall and use the equation F = ma and know that the force and the acceleration are in the same direction

 12 Describe, qualitatively, motion in a circular path due to a force perpendicular to the motion as:

 (a) speed increases if force increases, with mass and radius constant

 (b) radius decreases if force increases, with mass and speed constant

 (c) an increased mass requires an increased force to keep speed and radius constant

1.5.2 Turning effect of forces

 1 Describe the moment of a force as a measure of its turning effect and give everyday examples

 2 Define the moment of a force as moment = force × perpendicular distance from the pivot; recall and use this equation

 3 Apply the principle of moments to situations with one force each side of the pivot, including balancing of a beam

 4 State that, when there is no resultant force and no resultant moment, an object is in equilibrium

 5 Apply the principle of moments to other situations, including those with more than one force each side of the pivot

 6 Describe an experiment to demonstrate that there is no resultant moment on an object in equilibrium

1.5.3 Centre of gravity

 1 State what is meant by centre of gravity

 2 Describe an experiment to determine the position of the centre of gravity of an irregularly shaped plane lamina

 3 Describe, qualitatively, the effect of the position of the centre of gravity on the stability of simple objects

1.6 Momentum

 1 Define momentum as mass*velocity; recall and use the equation p = mv

 2 Define impulse as force*time for which force acts; recall and use the equation impulse = Ft = (mv)

 3 Apply the principle of the conservation of momentum to solve simple problems in one dimension

 4 Define resultant force as the change in momentum per unit time; recall and use the equation F = dp/ dt

1.7 Energy, work and power

1.7.1 Energy

 1 State that energy may be stored as kinetic, gravitational potential, chemical, elastic (strain), nuclear, electrostatic and internal (thermal)

 2 Describe how energy is transferred between stores during events and processes, including examples of transfer by forces (mechanical work done), electrical currents (electrical work done), heating, and by electromagnetic, sound and other waves

 3 Know the principle of the conservation of energy and apply this principle to simple examples including the interpretation of simple flow diagrams

 4 Recall and use the equation for kinetic energy Ek = 1/2mv2

 5 Recall and use the equation for the change in gravitational potential energy Ep = mgh

 6 Know the principle of the conservation of energy and apply this principle to complex examples involving multiple stages, including the interpretation of Sankey diagrams

1.7 Energy, work and power

1.7.2 Work

 1 Understand that mechanical or electrical work done is equal to the energy transferred

 2 Recall and use the equation for mechanical working W = Fd = DE

1.7.3 Energy resources

 1 Describe how useful energy may be obtained, or electrical power generated, from:

 (a) chemical energy stored in fossil fuels

 (b) chemical energy stored in biofuels

 (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams

 (d) geothermal resources

 (e) nuclear fuel

 (f) light from the Sun to generate electrical power (solar cells)

 (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy including references to a boiler, turbine and generator where they are used

 2 Describe advantages and disadvantages of each method in terms of renewability, availability, reliability, scale and environmental impact

 3 Understand, qualitatively, the concept of efficiency of energy transfer

 4 Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal

 5 Know that energy is released by nuclear fusion in the Sun

 6 Know that research is being carried out to investigate how energy released by nuclear fusion can be used to produce electrical energy on a large scale

 7 Define efficiency

1.7 Energy, work and power

1.7.4 Power

 1 Define power as work done per unit time and also as energy transferred per unit time; recall and use the equations (a) P = W/ t and (b) P=E/t

1.8 Pressure

 1 Define pressure as force per unit area; recall and use the equation p = F/A

 2 Describe how pressure varies with force and area in the context of everyday examples

 3 Describe, qualitatively, how the pressure beneath the surface of a liquid changes with depth and density of the liquid

 4 Recall and use the equation for the change in pressure beneath the surface of a liquid p = ρgh