In a collision between two objects, kinetic energy is conserved only if
In an elastic collision, both momentum and kinetic energy are conserved. In inelastic collisions, kinetic energy is not conserved as some is converted to other forms like heat or deformation. The initial rest state or potential energy conversion does not determine KE conservation.
The quantity of motion of a body is its
Momentum is defined as the product of mass and velocity (p = mv), representing the quantity of motion. Acceleration is rate of velocity change, displacement is position change, and velocity is speed with direction.
The volume of a fixed mass of a gas varies inversely as the pressure on it, provided the temperature is constant. This statement is
Boyle's law states that for a fixed mass of gas at constant temperature, pressure (P) times volume (V) is constant (PV = constant), or V ∝ 1/P. Charles' law relates V to T at constant P, pressure law to P and T at constant V, and general gas law combines all three.
An image formed on a screen is always
Real images, which can be projected on a screen, are formed by converging rays and are always inverted relative to the object. Virtual images cannot be projected on a screen and are upright.
How would the capacitance of a parallel plate capacitor be affected if the distance of separation of its plates is decreased? It will
Capacitance C = ε₀A/d, where d is plate separation. Decreasing d inversely increases C, as the electric field strength increases for the same charge.
Which of the following machines does not apply the lever principle?
A single pulley operates on the principle of redirecting force via a rope over a wheel, not leveraging a fulcrum, effort, and load like the other options, which are all class 1, 2, or 3 levers.
The average distance moved by a molecule between collisions is called
The mean free path is the average distance a molecule travels between successive collisions with other molecules in a gas, depending on density and molecular size.
Which of the following waves requires a material medium for its propagation?
Sound waves are mechanical longitudinal waves that require a material medium (solid, liquid, or gas) to propagate by vibrating particles. Electromagnetic waves (A, B, D) propagate through vacuum.
The depolarizing agent in a Leclanche cell is
Manganese(IV) oxide (MnO₂) acts as the depolarizer in a Leclanche cell by oxidizing the hydrogen gas produced at the cathode, preventing polarization and maintaining voltage.
The material used to slow down the neutrons in a nuclear reactor is
Graphite serves as a moderator in nuclear reactors, slowing fast neutrons via elastic collisions to increase fission probability in U-235. Boron absorbs neutrons, copper is not typically used, uranium is fuel.
Which of the following statements explains why hot soapy water is more effective in cleaning oil-stained dishes?
Soap acts as a surfactant, reducing the surface tension of water to allow better wetting and emulsification of oil droplets. Heat further lowers surface tension, improving cleaning efficiency.
A beam consisting of α-particles, β-particles, and γ-rays passes through a magnetic field at right angles to the direction of the field. What observation would be made about α-particles, β-particles, and γ-rays respectively?
Charged particles (α positive, β negative) experience Lorentz force F = q(v × B), deflecting them in opposite directions. Neutral γ-rays (photons) are undeflected.
An electrical device has 50 turns in its primary coil and 20 turns in the secondary coil; the device can be an
In a transformer, V_s / V_p = N_s / N_p. With N_s (20) < N_p (50), V_s < V_p, stepping down voltage. Generators do not use primary/secondary coils in this context.
The earpiece of a telephone handset converts energy from
The earpiece (speaker) converts electrical signals from the telephone line into sound waves via electromagnetic or piezoelectric transduction for the listener to hear.
Two identical cups containing the same volume of water at 45°C and 5°C are left in a room at 25°C. Which process best describes the temperature change?
Both cups will exchange heat with the room until thermal equilibrium at 25°C via conduction and convection. The hot water cools gradually, the cold warms gradually; overall, temperatures approach room temperature asymptotically (Newton's law of cooling).
A ray of light traveling from glass into ethyl alcohol is incident at the boundary at an angle of incidence 30°. Calculate the angle of refraction. (Refractive index of glass = 1.5; refractive index of ethyl alcohol = 1.36)
Using Snell's law: n₁ sin i = n₂ sin r → sin r = (n₁ / n₂) sin i = (1.5 / 1.36) × sin 30° ≈ 1.1029 × 0.5 = 0.55145 → r = sin⁻¹(0.55145) ≈ 33.5°. Light bends away from normal entering less dense medium (n_glass > n_alcohol).
A 60 kg man stands on a weighing balance in an elevator. If the elevator accelerates upwards at 5 ms⁻², determine the reading of the scale (g = 10 ms⁻²)
Apparent weight = m(g + a) = 60 × (10 + 5) = 900 N. Upward acceleration increases normal force from scale.
The length of an iron bar is 100 cm at 20°C. At what temperature will its length increase by 0.01%? (Linear expansivity of iron = 1.2 × 10⁻⁵ °C⁻¹)
ΔL / L = α ΔT → 0.0001 = 1.2 × 10⁻⁵ ΔT → ΔT = 0.0001 / 1.2 × 10⁻⁵ ≈ 8.33°C → T = 20 + 8.33 ≈ 28.3°C.
A moving-coil galvanometer which gives a full-scale deflection with 0.005 A is converted to a voltmeter, reading up to 5 V using an external resistance of 975 Ω. What is the resistance of the meter?
Total resistance R_total = V / I_g = 5 / 0.005 = 1000 Ω. Meter resistance R_m = R_total - R_external = 1000 - 975 = 25 Ω.
A parallel plate capacitor is charged and the charging battery subsequently disconnected. If the plates of the capacitor are moved farther apart by means of insulating handles, the capacitance would
With battery disconnected, charge Q is constant. C = ε₀A/d; increasing d decreases C. Potential difference V = Q/C increases, but options A/C/D incorrect; B correct for capacitance.
The velocity of sound in air at 15°C is 340 ms⁻¹. Calculate the velocity at 47°C
v ∝ √T (Kelvin): v₂ = v₁ √(T₂ / T₁) = 340 √((47+273)/(15+273)) = 340 √(320/288) ≈ 340 × 1.0536 ≈ 358 ms⁻¹.
Which of the current-voltage characteristics is exhibited by an ohmic conductor?
Ohmic conductors obey Ohm's law (V = IR), yielding a straight-line I-V graph through origin with constant slope (1/R). Non-ohmic show curves.
A 500 N box rests on a horizontal floor. A constant horizontal force is applied to move it. If the coefficient of friction is 0.2, what is the minimum force required to start motion? (g = 10 ms⁻²)
Weight W = 500 N (m = 50 kg). Frictional force f = μN = 0.2 × 500 = 100 N. Minimum force to overcome static friction is 100 N.
The normal force on an object on an inclined plane is
Normal force N perpendicular to plane balances mg cos θ component, so N = mg cos θ.
The net force on an object along an inclined plane with an applied force F is
Assuming F parallel up the plane, net force down = mg sin θ - F (if F < mg sin θ). (Context implies overcoming gravity component.)
What factors determine the frequency of a note emitted by a vibrating string?
Fundamental frequency f = (1/(2L)) √(T/μ), where L = length, T = tension, μ = mass per unit length. Amplitude affects loudness, not frequency.
The magnitude of the force experienced by a charge of 1.6 × 10⁻⁸ C in a uniform electric field of intensity 5 × 10⁵ N C⁻¹ is
F = qE = 1.6 × 10⁻⁸ × 5 × 10⁵ = 8.0 × 10⁻³ N.
Which of the following statements about viscosity is not true? It
Viscosity η = (F/A) / (dv/dx); it depends on velocity gradient (relative velocity between layers). Coefficient η is independent of area and force but force depends on η.
A motorcycle starting from rest is uniformly accelerated such that its velocity in 10 s is 72 km hr⁻¹. What is its acceleration?
v = 72 km/h = 20 m/s, u = 0, t = 10 s → a = (v - u)/t = 20/10 = 2 m s⁻².
The temperature of an object is raised by 120°C. The resulting increase in its absolute temperature is
ΔT in Celsius equals ΔT in Kelvin, as absolute scale shift is constant. Increase of 120°C = 120 K.
Which of the following statements about the motion of a simple pendulum is true?
Effective g is greater at poles (no centrifugal reduction) than equator, so T = 2π √(L/g) smaller, frequency higher (swings faster). SHM approximation for small angles (A false), max speed/KE at equilibrium (B/C false).
An electron of mass m and charge e moves in a circular path in a magnetic field of flux density B. How long does it take to complete one orbit?
Cyclotron period T = 2π m / (B e), from centripetal force = magnetic force: m v² / r = B e v → angular frequency ω = B e / m → T = 2π / ω = 2π m / (B e).
Which of the following statements about photoelectrons is correct?
KE_max = h f - φ; f_green > f_red, so higher KE for green regardless of intensity (which affects number, not KE). Faint green still higher f than bright red.
In the hydraulic press, the force F applied is related to the diameter d of the cylinder by
Pascal's principle: P = F₁/A₁ = F₂/A₂; A ∝ d², so for constant P, F ∝ A ∝ d².
In an electric circuit, an inductor of inductance 0.5 H and resistance 50 Ω is connected to an alternating current source of frequency 60 Hz. Calculate the impedance of the circuit.
Z = √(R² + X_L²), X_L = 2π f L = 2π × 60 × 0.5 ≈ 188.5 Ω → Z = √(50² + 188.5²) ≈ 195 Ω.
Which of the following statements correctly explains why a total solar eclipse would be seen by people on only a small portion of the earth’s surface? The
The moon's smaller size casts a small umbra shadow on Earth, covering only a narrow path for totality. Larger Earth relative to moon limits the eclipse visibility area.
Water waves have a wavelength of 3.6 cm and speed of 18 cm s⁻¹ in deep water. If the waves enter shallow water with wavelength of 2.0 cm, calculate the speed of the waves in the shallow water
Frequency f constant: f = v_deep / λ_deep = v_shallow / λ_shallow → v_shallow = 18 × (2.0 / 3.6) = 10 cm s⁻¹. Speed decreases in shallow water as λ shortens.
An a.c. generator can be converted to a d.c. electric motor by replacing the
Replacing slip rings (for AC output) with split-ring commutator rectifies to DC, and connecting a DC battery provides input for motor operation, reversing current direction every half-turn for continuous torque.
A ray of light travels obliquely from a less dense medium to a denser medium. Which of the following statements is true about the light?
Entering denser medium (higher n), light slows (v = c/n decreases), λ decreases (λ = v/f), bends towards normal (Snell's law). Frequency f constant.
What is the efficiency of a machine that does 500 J of useful work when 600 J of energy is supplied?
Efficiency η = (useful work output / energy input) × 100% = (500 / 600) × 100% ≈ 83.3%. Accounts for energy losses as heat/friction.
Now practice in exam mode
You've studied the answers — now test yourself under real exam conditions with the timer running.
Start WAEC Physics 2020 Quiz