3.1  Motion


3.1.1  Kinematics

(a) displacement, instantaneous speed, average speed, velocity and acceleration

These should be familiar from GCSE.  You need to be able to quote definitions for all of them.



(b) graphical representations of displacement, speed, velocity and acceleration


(c) Displacement–time graphs; velocity is gradient


(d) Velocity–time graphs; acceleration is gradient; displacement is area under graph.


This means draw speed time and displacement time graphs.  You should already know the basics but you do need to think about things like negative velocity if something has changed direction.



3.1.2  Linear Motion


Learners should be able to demonstrate and apply their knowledge and understanding of:


(a) (i) the equations of motion for constant acceleration in a straight line, including motion of bodies falling in a uniform gravitational field without air resistance

These are important and come up on every exam paper.  They can seem difficult at first, but you should soon get the hang of them.  You need to know three things in order to find the others.  Key points to remember:  if it starts from rest then u=0.  If it stops, then v=0.  If acceleration and velocity are in opposite directions then one of them must be negative.



(ii) techniques and procedures used to investigate the motion and collisions of objects PAG1 Apparatus may include trolleys, air-track gliders, ticker timers, light gates, data-loggers and video techniques.



(b) (i) acceleration g of free fall

If dropped, all objects accelerate at the same rate i.e. 9.81 m/s2 if there is no air resistance.

This seems weird because on Earth there is always air resistance.  However, questions often state to ignore it so everything accelerates at the same rate.



(ii) techniques and procedures used to determine the acceleration of free fall using trapdoor and electromagnet arrangement or light gates and timer

PAG Determining g in the laboratory.

There are lots of different ways to determine 'g'.  We will do lots of them in class as a PAG.  You will need to be able to talk about errors and uncertainties in each experiment.



(c) reaction time and thinking distance; braking distance and stopping distance for a vehicle.

The concepts and definitions have not changed since GCSE and you still need them.  You will also be required to apply the suvat equations above to solving problems about stopping.






3.1.3  Projectile Motion

Learners should be able to demonstrate and apply their knowledge and understanding of:


(a) independence of the vertical and horizontal motion of a projectile

This is what is proved by the monkey and hunter experiment (see video).  It has far reaching implications and is what you assume every time you do a projectile problem.  It is not just vertical and horizontal.  Any two directions that are perpendicular to each other can be considered independent.



(b) two-dimensional motion of a projectile with constant velocity in one direction and constant acceleration in a perpendicular direction.

Again, these questions can seem daunting at first, but they are all the same and practice makes perfect.  Remember that if the acceleration and velocity are in opposite directions, then they need to have opposite signs.  There is no hard and fast rule about which way is positive - it depends on the situation.