### Mr Cowen’s definitive definitions for Newtonian World

### Mr Godfrey’s June 2011 Newtonian World walkthrough

### Revision videos

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#### Module 1: Newton’s laws and momentum

**4.1.1 Newton’s laws of motion**

(a) state and use each of Newton’s three laws of motion;

(b) define *linear momentum* as the product of mass and velocity and appreciate the vector nature of momentum;

(c) define *net force on a body* as equal to rate of change of its momentum;

(d) select and apply the equation to solve problems;

(e) explain that is a special case of Newton’s second law when mass *m* remains constant;

(f) define *impulse of a force*;

(g) recall that the area under a force against time graph is equal to impulse;

(h) recall and use the equation .

**4.1.2 Collisions**

(a) state the principle of conservation of momentum;

(b) apply the principle of conservation of momentum to solve problems when bodies interact in one dimension;

(c) define a *perfectly elastic collision* and an *inelastic collision*;

(d) explain that whilst the momentum of a system is always conserved in the interaction between bodies, some change in kinetic energy usually occurs.

#### Module 2: Circular motion and oscillations

**4.2.1 Circular motion**

(a) define the *radian*;

(b) convert angles from degrees into radians and vice versa;

(c) explain that a force perpendicular to the velocity of an object will make the object describe a circular path;

(d) explain what is meant by centripetal acceleration and centripetal force;

(e) select and apply the equations for speed

and centripetal acceleration

(f) select and apply the equation for centripetal force

**4.2.2 Gravitational fields**

(a) describe how a mass creates a gravitational field in the space around it;

(b) define *gravitational field strength* as force per unit mass;

(c) use gravitational field lines to represent a gravitational field;

(d) state Newton’s law of gravitation;

(e) select and use the equation for the force between two point or spherical objects;

(f) select and apply the equation for the gravitational field strength of a point mass;

(g) select and use the equation to determine the mass of the Earth or another similar object;

(h) explain that close to the Earth’s surface the gravitational field strength is uniform and approximately equal to the acceleration of free fall;

(i) analyse circular orbits in an inverse square law field by relating the gravitational force to the centripetal acceleration it causes;

(j) define and use the *period* of an object describing a circle;

(k) derive the equation from first principles;

(l) select and apply the equation for planets and satellites (natural and artificial);

(m) select and apply Kepler’s third law to solve problems;

(n) define *geostationary orbit* of a satellite and state the uses of such satellites.

**4.2.3 Simple harmonic oscillations**

(a) describe simple examples of free oscillations;

(b) define and use the terms *displacement*, *amplitude*, *period*, *frequency*, *angular frequency* and *phase difference*;

(c) select and use the equation

(d) define *simple harmonic motion*;

(e) select and apply the equation as the defining equation of simple harmonic motion;

(f) select and use or as solutions to the equation ;

(g) select and apply the equation for the maximum speed of a simple harmonic oscillator;

(h) explain that the period of an object with simple harmonic motion is independent of its amplitude;

(j) describe and explain the interchange between kinetic and potential energy during simple harmonic motion;

(k) describe the effects of damping on an oscillatory system;

(l) describe practical examples of forced oscillations and resonance;

(m) describe graphically how the amplitude of a forced oscillation changes with frequency near to the natural frequency of the system;

(n) describe examples where resonance is useful and other examples where resonance should be avoided.

#### Module 3: Thermal physics

**4.3.1 Solid, liquid or gas**

(a) describe solids, liquids and gases in terms of the spacing, ordering and motion of atoms or molecules;

(b) describe a simple kinetic model for solids, liquids and gases;

(c) describe an experiment that demonstrates Brownian motion and discuss the evidence for the movement of molecules provided by such an experiment;

(d) define the term *pressure* and use the kinetic model to explain the pressure exerted by gases;

(e) define *internal energy* as the sum of the random distribution of kinetic and potential energies associated with the molecules of a system;

(f) explain that the rise in temperature of a body leads to an increase in its internal energy;

(g) explain that a change of state for a substance leads to changes in its internal energy but not its temperature;

(h) describe using a simple kinetic model for matter the terms melting, boiling and evaporation.

**4.3.2 Temperature**

(a) explain that thermal energy is transferred from a region of higher temperature to a region of lower temperature;

(b) explain that regions of equal temperature are in thermal equilibrium;

(c) describe how there is an absolute scale of temperature that does not depend on the property of any particular substance (ie the thermodynamic scale and the concept of absolute zero);

(d) convert temperatures measured in kelvin to degrees Celsius (or vice versa):

;

(e) state that absolute zero is the temperature at which a substance has minimum internal energy.

**4.3.4 Ideal gases**

(a) state Boyle’s law;

(b) select and apply ;

(c) state the basic assumptions of the kinetic theory of gases;

(d) state that one mole of any substance contains particles and that is the Avogadro constant ;

(e) select and solve problems using the ideal gas equation expressed as

and ,

where *N* is the number of atoms and *n* is the number of moles;

(f) explain that the mean translational kinetic energy of an atom of an ideal gas is directly proportional to the temperature of the gas in kelvin;

(g) select and apply the equation for the mean translational kinetic energy of atoms.