Mechanics
Forces, moments, mass and weight, speed, work, energy and power, at Level 1.
Mechanics (Cat A), summary notes
- A force is a push or a pull, measured in newtons (N). A moment is a force's turning effect about a pivot.
- Mass (kg) is the amount of matter in a body and never changes; weight (N) is the pull of gravity on that mass and changes with location.
- Speed is distance ÷ time; velocity is speed in a given direction; acceleration is the rate of change of velocity.
- Work is done when a force moves through a distance. Power is the rate of doing work. Energy is the capacity to do work and is conserved, it only changes form.
- Friction always opposes motion. A body is in equilibrium when the forces and moments on it balance.
- Moment
- M = F × d
- Weight
- W = m × g (g ≈ 9.81 m/s²)
- Speed
- speed = distance ÷ time
- Work
- W = F × d
- Power
- P = W ÷ t
- Kinetic energy
- KE = ½mv²
- Potential energy
- PE = mgh
A force of 100 N acts 2 m from a pivot. What moment does it produce?
M = F × d = 100 × 2 = 200 N·m.
A crate is lifted by a 10 N force through a height of 3 m. How much work is done?
W = F × d = 10 × 3 = 30 J.
Kinetics in 3D, linear, rotational & periodic motion
Newton's second law, F = ma
Moments & equilibrium
Levers & mechanical advantage
Friction, static & kinetic
Work, energy & power
Projectile motion
Energy conversion (KE ⇄ PE)
Mechanics concept map
Statics & Dynamics
Mechanics quiz
Mechanics (Cat A)
1. A force is a:
Push or pullType of energyUnit of mass2. The SI unit of force is the:
NewtonJouleWatt3. The turning effect of a force is called a:
MomentVelocityDensity4. Moment equals force multiplied by:
Perpendicular distanceTimeMass5. A 100 N force acting 2 m from a pivot gives a moment of:
200 N·m50 N·m102 N·m6. Weight is the force due to:
GravityFrictionMagnetism7. Mass is measured in:
KilogramsNewtonsMetres8. Weight is measured in:
NewtonsKilogramsLitres9. On the Moon, an object's mass:
Stays the sameDecreasesIncreases10. Speed equals distance divided by:
TimeMassForce11. The SI unit of speed is:
Metres per secondNewtonsJoules12. A car travels 100 m in 5 s. Its speed is:
20 m/s500 m/s0.05 m/s13. Velocity is speed in a given:
DirectionTimeMass14. Acceleration is the rate of change of:
VelocityDistanceMass15. The SI unit of acceleration is:
m/s²m/sN