2025 Montfort Physics Formula List 6091

SYLLABUS 6091 PHYSICS G3 YEAR 2024LIST OF EQUATIONS NO. EQUATION MEANING OF SYMBOLS Example Solution GENERAL PHYSICS 1 a = Δ v / Δ t = (v – u) / t a = instantaneous acceleration in m/s2 ; v = final velocity ; u = initial velocity ; t = time taken in s A car accelerates uniformly from 20 m/s to 30 m/s. During this acceleration, the car travels 100m. The average speed is 25 m/s. What is the acceleration of this car? ** t = 4.0 s in this question based on formula (3) average speed. = 2.5 m/s2 2 Distance travelled = area under graph The graph represents the movement of a car. How far has the car moved between 0 and 5.0 s? Distance travelled = area under graph = ½ x 5.0 x 10 = 25 m 3 A car takes half an hour to travel 7.0 km from A to B. What is its average speed? = 14 km/h4 F = ma Fresultant = Fapplied – Fopposing resultant is also known as netfriction, air resistance are possible FopposingF = resultant force in N ; m = mass in kg ; a = acceleration in m/s2 A boy pushes a box of mass 20 kg with a force of 50 N at constant speed. When the force is increased to 80N, what is the acceleration of the box? Frictional force = 50 N Resultant force = 80 N – 50 N F = ma 80 – 50 = 20 (a) a = 1.5 m/s2

5 ρ ρ = density in kg/m3 ; m = mass in kg ; V = volume in m3 Given that a wooden cube of length 8.0 cm has a mass of 500 g, calculate the density of the wood in g cm-3. ρ = 0.97656 ≈ 0.98 or 0.977 g / cm3 6 w = mg w = weight in N ; m = mass in kg ; g = gravitational field strength in N/kg The acceleration of free fall on the Moon is 1.6 ms-2. The acceleration of free fall on Earth is 10 ms-2. A rock has a mass of 10 kg on Earth. Calculate the weight of the rock on (a) on Earth (b) on the Moon. (a)w = mg = (10)(10) = 100 N (b)w = mg = (10)(1.6) = 16 N 7 Moment = F x d F = force in N ; d = perpendicular distance from the line of action of F to the pivot in m A door is hinged at its edge. A girl opens it by exerting a force of 10 N on the door handle located at the other end. Determine the moment due to the force exerted by the girl on the door. Moment = F × d = 10 N × 1.0 m = 10 N m 8 W = F x s [use if F is constant] W = work done in J ; F = force in N ; s = distance moved in the direction of F in m A boy pushes a box across a rough horizontal floor. He exerts 5.0 N to move it 2.0 m. What is the work done by the 5.0 N force? W = F × s = 5.0 x 2.0 = 10 J 9 P orP P = power in W ; W = work done in J ; t = time in s ; E = energy converted An engine does 60 000 J of work in ten minutes. Determine its power. * 1 W = 1 J/s so the time must be expressed in seconds for it to be converted to Watts (W)P = 100 W 10 Ep = mgh Ep = energy in gravitational potential store in J ; m = mass in kgg = 10 N/kg gravitational field strength on earth; h = vertical distance in m A 5.0 kg box is raised 50 m from its original position. What is the gain in energy in the gravitational potential store? Ep = mgh = (5)(10)(50) = 2500 J

11 Ek = ½ mv2 Ek = energy in kinetic store in J ; m = mass in kg ; v = speed in m/s A 50 g toy car is moving at a constant speed of 2.0 m s−1. Determine its energy in it kinetic store KE = ½ mv2 = 0.10 J 12EnergyPowerA motor with a power rating of 500 W pulls up a block of weight 20 N by 3.0 m every second.Calculate its efficiency. E = Pt= 500 W (1s) = 500 J Work done = F x s = 20 N x (#.0 m) = 60 J = 0.12 If in percentage, % efficiency = 0.12 x 100% = 12%13p = pressure in Pa (or N/m2) ; F = normal force in N ; A = area in m2 A student of weight 800 N stands on an area of 250 x 10-4 m2. Calculate the pressure exerted by her feet on the ground. Pa or N/m2

14 p = hρgBarometer p = pressure in Pa (or N/m2) ; h = height in m ; ρ = density of the liquid in kg/m3 g = gravitational field strength in N/kg Manometer Calculate the pressure on a fish 10 m below the water surface and where the atmospheric pressure above the surface is 760 mmHg.Taking that the density of water is 1000 kg/m3g is 10 N/kg,density of mercury is 13 600 kg/m3 760 mm Hg is one atmospheric pressure which is the pressure exerted by Earth’s atmosphere. It means it is the pressure equivalent to 760 mm height of mercury (Hg)Pressure due to water only:p = hρg = 10 x 1000 x 10 = 100 000 PaPressure due to atmosphere isp = hρg = (760/1000) x 13600 x 10 = 103, 360 Pa ≈ 103 000 PaTotal pressure = 100 000 + 103 000= 103 000 Pa 15 = the force applied on piston 1 = the force applied on piston 2 = the area of piston 1 = the area of piston 2Hydraulic PressA force of 50 N is applied on piston 1 with an area of 0.0025 m2. Piston 2 has an area of 0.25 m2. Calculate the force on piston 2. 5000 N

THERMAL 16Q = mcΔθQ = CΔθwhere C = mcQ = change in internal energy by energy transfer / energy transferred by heating in Jm = mass in kgc = specific heat capacity in J/kgoC or J/kgKC = mc = heat capacity J/oC or J/KΔθ = change in temperature oC or K (where Δ represents change and θ temperature) A substance of mass 2.0 kg has specific heat capacity of 4200 J/kgoC and rose by 12 oC.Calculate the heat capacity.Calculate the rise in internal energy (by energy transfer). C = mc= 2.0 (4200)= 8400 J/oC Q = CΔθ = 8400 (12) = 100,800 J ≈ 100 000 J (2 sf) or 101 000 J (3 sf)17Q = mlL = mlQ = change in internal energy by energy transfer / energy transferred by heating in Jm = mass in kgl = specific latent heat in J/kg or J/kgL = latent heat in JQ or L can be used with respect to the context of the question1000 J of energy was supplied to pure ice at 0 oC of mass m to melt it fully to water at 0 oC.The latent heat of fusion is 334 J/g.Calculate the mass of ice in g that melted.Q = m lf1000 J = m (334 J/g)m = 2.994 g ≈ 3.0 g

Additionally a subscript f and v represents fusion and vaporization respectively.E.g. lv = the specific latent heat of vaporizationLIGHT, WAVES and SOUND 18n = refractive index (from vacuum to medium); i = angle of incidence (in vacuum/air) ; r = angle of refraction (in medium) A ray of light is incident from the water to the air at an angle of 40. The refractive index of water is 1.33. Calculate the angle of refraction. = 1.33 sin 40o 58.7o 19 n = refractive index (from vacuum to medium); c – critical angle Find the critical angle of the glass of refractive index 1.5. 41.8o 20 = velocity of light in vacuum (3.0 × 108 m/s); = velocity of light in the second optical medium Calculate the speed of light in diamond of refractive index 2.4. m/s 21 v = f λ = speed of wave in m/s ; = frequency in Hz ; λ = wavelength in m A bat makes a sound that is higher than the maximum audible frequency of human beings. Given that the * max audible frequency is f = 20000 Hz

speed of sound in air is 300 m/s. What is the maximum wavelength of the sound? v = f λ 300 = (20000) λ λ = 0.015 m 22 = frequency in Hz ; = period in s The period of a waveform is 0.50 s. What is the frequency? Hz 23 Echolocation = speed of sound in medium = distance from the source of sound to thepoint of reflection e.g. wall.d The sonar of a ship sends out a signal which is reflected and returns back to the sonar after hitting an object. The time taken between the start of the signal and when the echo is received is 40 ms.Take speed of sound in water as 1500 m/s.40 ms = 0.040 s mELECTRICITY and MAGNETISM

24 = electric current in A; = electric charge in C; = time in s Find the current when 10 C of charge flows through a resistor in 8.0 s. A 25 = potential difference, or = electromotive force (e.m.f.);= energy in J; = electric charge in CA lamp is connected to a battery in a circuit. The lamp gives off 12 J of energy when a charge of 5.0 C passes through