Physics Exam Notes

Movement and Position

  • Average speed is calculated as: v=stv = \frac{s}{t}
  • Units of speed include m/s and km/h.
  • To convert m/s to km/h, multiply by 3.6.
  • Distance can be calculated as: s=v×ts = v \times t
  • Time can be calculated as: t=svt = \frac{s}{v}
  • The slope of a distance-time graph indicates speed; a straight line signifies constant speed.
  • Displacement is distance in a specific direction; velocity is speed in a specific direction.
  • Average velocity is calculated as: average velocity = increase in displacement / time taken
  • Acceleration is the rate of change of velocity: a=v−uta = \frac{v - u}{t}, where v is final velocity and u is initial velocity.
  • Acceleration is measured in m/s². Deceleration is negative acceleration.
  • The gradient of a velocity-time graph represents acceleration.
  • The area under a velocity-time graph represents the distance traveled.
  • Key equation: \v^2 = u^2 + 2as

Forces and Shape

  • Forces can change an object's speed, shape, or direction.
  • Examples of forces include gravitational, electrostatic, and magnetic forces.
  • Force is a vector quantity measured in Newtons (N).
  • Resultant force: the vector sum of all forces acting on an object. An unbalanced force causes acceleration.
  • Friction opposes motion.
  • Hooke’s Law: Within the elastic limit, the extension of a spring is proportional to the applied force.

Forces and Movement

  • Relationship between force, mass, and acceleration: F=m×aF = m \times a
  • Weight is calculated as: W=m×gW = m \times g, where g is gravitational field strength (approximately 9.8 N/kg on Earth).
  • Stopping distance = thinking distance + braking distance
  • Factors affecting stopping distance: speed, mass, road conditions, and reaction time.
  • Falling objects reach terminal velocity when air resistance equals weight.

Momentum (Physics Only)

  • Momentum is calculated as: p=m×vp = m \times v
  • Force is related to change in momentum: F=mv−mutF = \frac{mv - mu}{t}, where mv is final momentum and mu is initial momentum.
  • In collisions, neglecting external forces, total momentum is conserved.
  • Newton’s Third Law: For every action, there is an equal and opposite reaction.

The Turning Effect of Forces (Physics Only)

  • Moment of a force = force × perpendicular distance from the pivot.
  • Weight acts through an object's centre of gravity.
  • The principle of moments: For an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments about a pivot.