m1

1. M1 exam technique – some key points
This document has been put together to try to counter common errors and to communicate the requirements
of Edexcel markschemes
Some General Points
1. Use phrases and words to explain what is going on e.g. position of B at time t is r =3i + 2j + t(-4i +j)
2. Always state the equation or principle you are using before you put in numbers e.g. v = u + at or
Conservation of momentum etc.
3. Whenever there are forces, always draw a diagram
4. When resolving, always start the line by explaining or stating what you are doing e.g. Res (->)
5. If something is in equilibrium, it is best to get all the forces (positive and negative) in the resolving, and then
put the sum of them equal to zero
6. “suvat” equations – a table is highly recommended – and remember to state a positive direction, especially for
questions about vertical motion
Some Common Errors
1. If it asks for speed, remember this is a scalar, so if you have a velocity vector, you will need to use Pythagoras
to find the magnitude.
2. Be careful when to use m and when to use mg. For example m (and then multiplied by velocity) for
momentum, but mg in any force situation, including when taking moments. And note carefully the difference
between mass and weight.
3. In momentum questions always do a clear 3 stage diagram (before, during- to show the impulses, and after)
and state a direction to be positive. Errors with plus and minus signs are very common.
4. Don’t forget to give suitable units for all answers.
5. Rounding to 3sf is often sensible, (but of course don’t round until the end so you avoid early rounding errors).
However, if you have used 9.8 for g somewhere in the method, then you should give your final answer to 2sf.
Points on certain topics
Vectors
1. If you are asked when something (e.g. A) is North of something else (e.g. B), or North East of something etc.,
then set the relative position vector (i.e. position of A relative to B) equal to k times a simple vector in that
direction and then equate the i components and the j components
e.g a vector in the direction of . Similarly a vector in the direction of .
2. Constant acceleration equations and F = ma work with vectors too
3. Position vector at time t is equal to (starting position vector at t = 0) + t×(velocity vector)
4. Distance between two ships at time t equals magnitude of difference between the two position vectors at time
t (often square root of a quadratic in t)
5. Minimum of this quadratic enables you to find smallest distance between the two ships, at a specific time
6. If minimum = 0 this means the ships crash (same position vector at the same time)

2. Graphs
1. The displacement of a particle can be found by considering the area enclosed by a velocity-time graph.
2. The acceleration can be found by calculating the gradient of a velocity-time graph
A
B
3. On this graph, the area of triangle A would give the displacement in the positive direction,
and the area of triangle B would give the displacement in the negative direction.
4. Total Displacement = Area of A - Area of B
5. Total Distance = Area of A + Area of B
6. The gradient of a displacement-time graph will give the velocity.
Constant Acceleration Formulae
1. Remember to learn the suvat equations
2. If you’re throwing an object up, then at v = 0 it reaches its maximum height
Moments
1. Moment = Force  Perpendicular Distance
2. If a beam is in equilibrium, Forces up = Forces down and moments around ANY point sum to 0
3. Always draw accurate and clear diagrams, as you get new information don’t be afraid to redraw the diagram
4. Unknown lengths will be referenced from a point, taking moments around this point is often the easiest option
5. If you have several unknown forces, take moments around a point where one of these forces act, this force
now has zero turning affect
6. If a beam is about to tip it’s about to lift off a support, the reaction force at this support is therefore 0
7. Modelling as a particle = force acts in one place, modelling as a beam = beam doesn’t bend
Connected Particles
1. Remember you can form equations of motion, for each particle (in each perpendicular direction) and one for
the whole system if it is all in a straight line.
2. Begin by drawing diagrams to show the forces on each of the bodies.
3. For connected particles a ≠ 9.8ms
-1
, but once a string has snapped particles in free fall will then have
a = 9.8ms
-1
(those on planes will not)
4. Light inextensible string = particles travel at the same velocity, and same acceleration
5. Smooth pulley = string has the same tension either sides of the pulley