P2: Forces

P2.1 Motion

PM2.1i recall and apply distance travelled (m) = speed (m/s) x time (s).

PM2.1ii recall and apply acceleration (m/s2) = change in speed (m/s) / time (s).

PM2.1iii apply (final velocity (m/s))2 – (initial velocity (m/s))2 = 2 x acceleration (m/s2) x distance (m).

PM2.1iv recall and apply kinetic energy (J) = 0.5 x mass (kg) x (speed (m/s))2.

P2.1a describe how to measure distance and time in a range of scenarios

P2.1b describe how to measure distance and time and use these to calculate speed

P2.1c make calculations using ratios and proportional reasoning to convert units and compute rates (M1c, M3c)

P2.1d explain the vector-scalar distinction as it applies to displacement and distance, velocity and speed

P2.1e relate changes and differences in motion to appropriate distance-time, and velocity-time graphs, and interpret lines, slopes and enclosed areas in such graphs

P2.1f interpret enclosed area in velocity-time graphs (M4a, M4b, M4c, M4d, M4f)

P2.1g calculate average speed for non-uniform motion (M1a, M1c, M2b, M3c)

P2.1h apply formulae relating distance, time and speed, for uniform motion, and for motion with uniform acceleration (M1a, M1c, M2b, M3c)

P2.2 Newton’s Laws

PM2.2i recall and apply force (N) = mass (kg) x acceleration (m/s2)

PM2.2ii recall and apply momentum (kgm/s) = mass (kg) x velocity (m/s)

PM2.2iii recall and apply work done (J) = force (N) x distance (m) (along the line of action of the force)

PM2.2iv recall and apply power (W) = work done (J) / time (s)

P2.2a recall examples of ways in which objects interact

P2.2b describe how such examples involve interactions between pairs of objects which produce a force on each object; represent such forces as vectors

P2.2c represent such forces as vectors

P2.2d apply Newton’s First Law to explain the motion of an object moving with uniform velocity and also an object where the speed and/or direction change

P2.2e use vector diagrams to illustrate resolution of forces, a net force, and equilibrium situations

P2.2f describe examples of the forces acting on an isolated solid object or system

P2.2g describe, using free body diagrams, examples where two or more forces lead to a resultant force on an object

P2.2h describe, using free body diagrams, examples of the special case where forces balance to produce a resultant force of zero(qualitative only)

P2.2i apply Newton’s Second Law in calculations relating forces, masses and accelerations

P2.2j explain that inertia is a measure of how difficult it is to change the velocity of an object and that the mass is defined as the ratio of force over acceleration

P2.2k define momentum and describe examples of momentum in collisions

P2.2l apply formulae relating force, mass, velocity and acceleration to explain how the changes involved are inter-related

P2.2m use the relationship between work done, force and distance moved along the line of action of the force and describe the energy transfer involved

P2.2n calculate relevant values of stored energy and energy transfers; convert between newton-metres and joules (M1c, M3c)

P2.2o explain, with reference to examples, the definition of power as the rate at which energy is transferred

P2.2p recall and apply Newton’s Third Law

P2.2q explain why an object moving in a circle with a constant speed has a changing velocity (qualitative only)

P2.3 Forces in action

PM2.3i recall and apply: force exerted by a spring (N) = extension (m) x spring constant(N/m)

PM2.3ii apply: energy transferred in stretching (J)= 0.5 x spring constant (N/m) x (extension(m))2

PM2.3iii recall and apply: gravity force (N) = mass (kg) x gravitational field strength, g (N/kg)

PM2.3iv recall and apply: in a gravity field: potential energy (J) = mass (kg)x height (m) x gravitational field strength, g (N/kg)

PM2.3v recall and apply: pressure (Pa) = force normal to a surface (N) / area of that surface(m2)

PM2.3vi recall and apply: moment of a force (Nm)= force (N) x distance (m) (normal to direction of the force)

P2.3a explain that to stretch, bend or compress an object, more than one force has to be applied

P2.3b describe the difference between elastic and plastic deformation (distortions) caused by stretching forces

P2.3c describe the relationship between force and extension for a spring and other simple systems

P2.3d describe the difference between linear and non-linear relationships between force and extension

P2.3e calculate a spring constant in linear cases

P2.3f calculate the work done in stretching

P2.3g describe that all matter has a gravitational field that causes attraction, and the field strength is much greater for massive objects

P2.3h define weight, describe how it is measured and describe the relationship between the weight of an object and the gravitational field strength (g) (and) has a value of 10N/kg at the Earth’s surface

P2.3i recall the acceleration in free fall

P2.3j apply formulae relating force, mass and relevant physical constants, including gravitational field strength (g), to explore how changes in these are inter-related (M1c, M3b, M3c)

P2.3k describe examples in which forces cause rotation

P2.3l define and calculate the moment of the force in such examples

P2.3m explain how levers and gears transmit the rotational effects of forces

P2.3n recall that the pressure in fluids (gases and liquids) causes a net force at right angles to any surface

P2.3o use the relationship between the force, the pressure and the area in contact