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Topic 1 of 8 · Form 5

Physical quantities, kinematics and dynamics

SI base units, homogeneity of equations, estimates, scalars and vectors (resolving and adding), systematic and random errors, precision and accuracy, combining uncertainties (add absolute uncertainties for sums; add fractional uncertainties for products and quotients).

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  1. PDFPhysical quantities, kinematics and dynamics – Physics notes (Cambridge A Level)46.3 KB

Quantities and uncertainties

SI base units, homogeneity of equations, estimates, scalars and vectors (resolving and adding), systematic and random errors, precision and accuracy, combining uncertainties (add absolute uncertainties for sums; add fractional uncertainties for products and quotients).

Kinematics

Equations of uniformly accelerated motion; graphs; projectile motion (horizontal and vertical components independent); motion with air resistance (terminal velocity).

Worked example: A ball is thrown at 20 m s⁻¹ at 30° above the horizontal. Find the maximum height (g = 9.81 m s⁻²).

uᵧ = 10 m s⁻¹ → h = uᵧ²/(2g) = 100/19.62 = 5.10 m

Dynamics

Newton's laws; momentum p = mv; F = Δp/Δt; conservation of momentum; elastic and inelastic collisions (relative speed of approach = relative speed of separation for perfectly elastic collisions).

Worked example: A 0.5 kg ball moving at 6 m s⁻¹ collides elastically head-on with a stationary 0.5 kg ball. Find the velocities after collision.

Equal masses, elastic: velocities exchange → first ball stops; second moves at 6 m s⁻¹

Exam tip: Uncertainties in final answers are usually given to one significant figure.

Check yourself

  1. Find the percentage uncertainty in the area of a square of side (5.0 ± 0.1) cm.
  2. State Newton's second law in terms of momentum.
  3. What is conserved in an elastic collision that is not conserved in an inelastic one?
Show answers
  1. 2 × 2% = 4%
  2. The resultant force is equal to the rate of change of momentum.
  3. Total kinetic energy.
Next topicForces, energy, deformation of solids

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