Physics Formulae

A Level H2 Physics (9479) Formulae Formulae highlighted in yellow is given in the formula list. Topic 1: Measurements Absolute Uncertainty 𝑥 ± ∆𝑥 Δx is the absolute uncertainty of x. Δx to 1 s.f. x to same d.p. as Δx Fractional Uncertainty ∆𝑥 𝑥 Δx is the absolute uncertainty of x. Fractional and percentage uncertainty to 2 s.f. Percentage uncertainty ∆𝑥 𝑥 × 100% First Principles ∆𝑧 ≈ 1 2 (𝑧𝑚𝑎𝑥 − 𝑧𝑚𝑖𝑛) Δz is the uncertainty of quantity z. zmax is the maximum value of z. zmin is the minimum value of z. Topic 2: Kinematics Velocity 𝑣 = 𝑑𝑠 𝑑𝑡 v is the velocity (m s-1) s is the displacement (m) t is the time (s) Average velocity 𝑣𝑎𝑣 = ∆𝑠 𝑡𝑡𝑜𝑡𝑎𝑙 Acceleration 𝑎 = 𝑑𝑣 𝑑𝑡 v is the velocity (m s-1) a is the acceleration (m s-2) t is the time (s) Average acceleration 𝑎𝑎𝑣 = ∆𝑣 𝑡𝑡𝑜𝑡𝑎𝑙 Equations of motion 𝑣 = 𝑢 + 𝑎𝑡 s is the displacement (m) u is the initial velocity (m s-1) v is the final velocity (m s-1) a is the acceleration (m s-2) t is the time (s) 𝑣2 = 𝑢2 + 2𝑎𝑠 𝑠 = 1 2 (𝑢 + 𝑣)𝑡 𝑠 = 𝑢𝑡 + 1 2 𝑎𝑡2 Topic 3: Dynamics Linear Momentum 𝑝 = 𝑚𝑣 p is the linear momentum (kg m s-1) m is the mass of the object (kg) v is the velocity of the object (m s-1) Newton’s 2nd Law 𝐹𝑛𝑒𝑡 = 𝑑𝑝 𝑑𝑡 = 𝑚𝑎 Fnet is the resultant force (N) p is the linear momentum (kg m s-1) t is the time taken for the object to change momentum (s) m is the mass of the object (kg) a is the acceleration of the object (m s-2) Newton’s 2nd Law involving Flowing Mass 𝐹𝑛𝑒𝑡 = 𝑚 𝑡 ∆𝑣 Fnet is the resultant force (N) m is the mass of the object (kg) t is the time taken for the amount of mass to flow out (s) v is the velocity (m s-1) Impulse ∆𝑝 = ∫ 𝐹 𝑑𝑡 Fnet is the resultant force (N) p is the linear momentum (kg m s-1) t is the time taken for the object to change momentum (s)

Principle of Conservation of Linear Momentum 𝑚1𝑢1 + 𝑚2𝑢2 = 𝑚1𝑣1 + 𝑚2𝑣2 m1 and m2 are the masses of the 2 colliding objects u1 and u2 are the velocities of the objects before collision v1 and v2 are the velocities of the objects after collision Principle of Conservation of Kinetic Energy 1 2 𝑚1𝑢12 + 1 2 𝑚2𝑢22 = 1 2 𝑚1𝑣12 + 1 2 𝑚2𝑣22 m1 and m2 are the masses of the 2 colliding objects u1 and u2 are the velocities of the objects before collision v1 and v2 are the velocities of the objects after collision Speed of approach vs speed of separation 𝑢1 − 𝑢2 = 𝑣2 − 𝑣1 u1 and u2 are the velocities of the objects before collision v1 and v2 are the velocities of the objects after collision Topic 4: Forces Hooke’s Law 𝐹 = 𝑘𝑥 F is the force applied (N) k is the elastic spring constant (N m-1) x is the change in length (m) Pressure 𝑝 = 𝐹 𝐴 p is the pressure (N m-2) F is the force (N) A is the area (m2) 𝑝 = ℎ𝜌𝑔 p is the pressure (N m-2) h is the height of the liquid (m) ρ is the density of the liquid (kg m-3) g is the acceleration due to gravity (N kg-1) Upthrust 𝑈 = 𝜌𝑉𝑔 = 𝑚𝑔 U is the upthrust exerted by fluid on an object (N) ρ is the density of