1(c) Forces, movement, shape and momentum
Pearson Edexcel International GCSE Physics · 4PH1
Paper 2 | Whole paper: All content including bold P statements
What forces do to bodies: change their motion, change their shape, and — in the Paper 2 statements — transfer momentum and turn things about a pivot.
Specification coverage
Topic 1 Forces and motion (c) Forces, movement, shape and momentum — statements 1.11–1.36P (includes bold P statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2, AO3. Suggested learning time: 110 minutes.
Required knowledge
- The effects of forces between bodies: changes in speed, shape or direction
- Different types of force, such as gravitational and electrostatic
- How vector quantities differ from scalar quantities, and that force is a vector
- Calculate the resultant of forces acting along a line
- Friction as a force that opposes motion
- force = mass × acceleration
- weight = mass × gravitational field strength
- Hooke's law and the behaviour of springs, including the limit of proportionality
- Bold P statements: momentum = mass × velocity, conservation of momentum, force = change in momentum ÷ time, and the principle of moments
Required skills
- Draw and interpret free-body force diagrams
- Resolve a problem into balanced and unbalanced forces
- Apply conservation of momentum to collisions (Paper 2)
- Apply the principle of moments to a balanced beam (Paper 2)
- Describe and evaluate the required practical: Investigate how extension varies with applied force for helical springs, metal wires and rubber bands.
How it is examined
- Multiple-choice and short-answer recall
- Calculations using the specification's relationships
- Extended open-response applying the physics to an unfamiliar situation
- Practical questions on method, variables, results and sources of error
Common mistakes
- Confusing mass and weight. Mass is in kilograms and does not change with location; weight is a force in newtons and does.
- Assuming Hooke's law holds indefinitely. Beyond the limit of proportionality the graph curves and the relationship fails.
- Forgetting momentum is a vector. In a head-on collision one velocity must be negative.
- Taking the distance in a moment calculation along the beam rather than perpendicular to the force.