Impulse | Physics for GCSE/IGCSE - Year 11 PDF Download

Impulse

• When an unbalanced force acts on an object's mass, its momentum undergoes alteration.
• The impulse exerted by a force equals the force multiplied by the duration of its application, represented as
  impulse = force × change in time or impulse = FΔt.
• This impulse, denoted as Δp, is synonymous with the change in momentum experienced by the mass.
• The change in momentum can also be described as the difference between the final momentum (mv) and the initial momentum (mu), expressed as Δp = Δ(mv) or Δp = mv − mu.
• Here,
  'm' stands for mass in kilograms,
  'v' represents the final velocity in meters per second, and
  'u' indicates the initial velocity in meters per second.
• Thus, the overall equation can be succinctly stated as impulse = FΔt = Δp = mv − mu.
• In everyday scenarios, an instance of impulse can be observed when sheltering under an umbrella during rain compared to hail (frozen water droplets).
  • When rain strikes an umbrella, the water droplets typically scatter and drip off, resulting in minimal alteration in momentum.
  • Conversely, hailstones possess a greater mass and tend to rebound off the umbrella, causing a more significant change in momentum.
  • Consequently, the impulse experienced by an umbrella is higher in hail than in rain.
  • This implies that a greater force is necessary to maintain an umbrella's stability in hail compared to rain.

Since hailstones bounce back off an umbrella, compared to water droplets from rain, there is a greater impulse on an umbrella in hail than in rain

Force & Momentum

• Force can be described as the rate at which momentum changes in an object.
• The alteration in momentum is calculated as the final momentum subtracted by the initial momentum of the object.
• These concepts can be expressed as: