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LearnEdexcel4PH12017 specificationPaper 2P · Paper 2 (all content)Forces and motion

Paper 2P · Module

Forces and motion

6 subtopics≈ 180 min in total

Start the module: Physical quantities and measurement Open graphing calculator

Physical quantities and measurement
Every physical quantity is a number with a unit. Measure carefully, and measure many small things together to reduce errors. Scalars have size only; vectors have size and direction, so two vectors at right angles combine by Pythagoras.
≈ 25 min
Speed, velocity and acceleration
Speed is distance per unit time; velocity is speed in a given direction. Acceleration is the rate of change of velocity. On a distance–time graph the gradient is speed; on a speed–time graph the gradient is acceleration and the area underneath is the distance travelled.
≈ 35 min
Forces and motion
If the forces on an object are balanced, it stays at rest or keeps moving at constant velocity. An unbalanced (resultant) force makes it accelerate: $F=ma$ . Friction and air resistance oppose motion, which is why a falling object reaches a terminal velocity. Moving in a circle needs a force towards the centre.
≈ 35 min
Springs and Hooke's law
A spring stretches in proportion to the load on it, $F=kx$ , up to the limit of proportionality. The spring constant $k$ tells you how stiff it is. Extension is measured from the original length, and a load–extension graph is a straight line through the origin until the limit is passed.
≈ 25 min
Turning effect and centre of gravity
A force can turn an object about a pivot: its moment is force $\times$ perpendicular distance from the pivot. When an object balances, the total clockwise moment equals the total anticlockwise moment. An object's weight acts at its centre of gravity; a low centre of gravity and wide base make it stable.
≈ 30 min
Momentum and impulse
Momentum is mass times velocity, $p=mv$ , and it has a direction. In any collision or explosion with no external force, the total momentum before equals the total after. A force changes momentum: $F=\dfrac{\Delta p}{\Delta t}$ , so spreading a change over a longer time means a smaller force.
≈ 30 min