1. In equilibrium, the resultant force is what?
- Zero
- Equal to weight always
- Equal to mass
Check the answer and reasoning
Zero
Zero resultant means no acceleration, though the particle may move at constant velocity.
MATH / AS level
Mechanics option: forces and motion
Mathematical mechanics models particles using kinematics, Newton’s laws, momentum, work and energy. A model may neglect size, air resistance or string mass.
Learning objectives
- Explain mechanics option: forces and motion using a concrete example.
- Apply the worked method and justify each step.
- Recognise the limitation described in the final check.
The big idea
Mathematical mechanics models particles using kinematics, Newton’s laws, momentum, work and energy. A model may neglect size, air resistance or string mass.
Resolve forces before applying F=ma. Constant-acceleration formulae require constant acceleration; energy methods are useful when time is not needed.
Equations and relationships
Straight-line motion with constant acceleration.
Worked example
A particle starts from rest, accelerating at 2 m/s² over 9 m. Find speed.
Follow the solution
v²=0+2×2×9=36, so speed is 6 m/s.
Investigate and explain
Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.
Related interactive model. Compare its assumptions with the explanation; it is not a complete syllabus lesson.
Check your understanding
2. A particle starts from rest, accelerating at 2 m/s² over 9 m. Find speed.
- 18 m/s
- 6 m/s
- 36 m/s
Check the answer and reasoning
6 m/s
v²=0+2×2×9=36, so speed is 6 m/s.
3. What is limiting friction for coefficient μ and normal force R?
- μ/R
- Always zero
- μR
Check the answer and reasoning
μR
μR is the maximum static friction; friction below the limit adjusts to the required value.