16 questions. Try each one, then open the answer to check yourself and read the explanation.
A waterfall is 42m high, calculate the difference in temperature of the water between the top and bottom of the waterfall assuming no heat is lost. [specific heat capacity of water = 4.20 × 103Jkg−1K−1, g = 10m/s2]
Answer: D (0.1°C)
Potential energy becomes heat: mgh = mcΔθ, so Δθ = gh/c = 10 × 42 ÷ 4200 = 0.1°C.
A body When slightly displaced is said to be in neutral equilibrium only if it tends to
Answer: A (come to rest in a new position with centre of - gravity and height remaining unchanged)
In neutral equilibrium (like a ball on a flat floor) a displaced body settles in its new position and its centre of gravity stays at the same height.
A string of length 5m is extended by 0.04m when a load of 0.8kg is suspended at the end. How far will it extend if a force of 16N is applied? [g = 10ms−2]
Answer: D (0.08m)
The load weighs 0.8 × 10 = 8 N. By Hooke's law extension is proportional to force, so 16 N (double) gives 2 × 0.04 = 0.08 m.
Which of the following has negligible mass?
Answer: B (Gamma rays)
Gamma rays are electromagnetic waves (photons) with no rest mass. Alpha and beta particles and protons all have mass.
How can energy loss be minimized through Eddy-current?
Answer: B (By using insulated soft iron wires)
Making the core from insulated soft-iron wires or laminations breaks up the paths of eddy currents, so less energy is wasted as heat.
Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density 103kgm−3. [g= 10ms−2]
Answer: C (0.5N)
Upthrust = ρVg = 1000 × 50 × 10−6 × 10 = 0.5 N.
Which of the following would appear when a white screen is illuminated by red and green light?
Answer: C (Yellow)
Adding the primary colours red and green light gives the secondary colour yellow.
Calculate the electric field intensity between two plates of potential difference 6.5V when separated by a distance of 35cm
Answer: A (18.57NC−1)
E = V/d = 6.5 ÷ 0.35 = 18.57 N/C (or V/m).
Find the potential energy of an object of mass 10kg placed on a building floor 10m above the ground level. [g = 10ms−2]
Answer: D (1,000J)
P.E. = mgh = 10 × 10 × 10 = 1000 J.
The volume of a fixed mass of gas is 10cm3 when its pressure is 400cmHg. Determine the volume of the gas when its pressure is 200cmHg.
Answer: D (20cm3)
Boyle's law: P1V1 = P2V2, so V2 = 400 × 10 ÷ 200 = 20 cm3.
What is the cost of running seven 40W lamps and five 80W lamps for 12 hours if the electrical energy costs ₦7 per kWh?
Answer: D (₦57.12)
Power = 7 × 40 + 5 × 80 = 680 W = 0.68 kW. Energy = 0.68 × 12 = 8.16 kWh. Cost = 8.16 × ₦7 = ₦57.12.
The thermal expansion of a solid is an advantage in
Answer: D (Fitting of tyres on wheels)
A metal tyre is heated so it expands, slipped onto the wheel, and grips tightly as it cools. In bridges, rail lines and watch balance wheels expansion is a problem to be allowed for.
Calculate the specific latent heat of vapourization of steam if 1.13 × 106J of heat energy is required to convert 15kg of water
Answer: C (7.53 × 104Jkg−1)
L = Q/m = 1.13 × 106 ÷ 15 = 7.53 × 104 J/kg.
A stationary wave pattern is formed by a wave of frequency 40Hz and velocity 60cms−1. What is the distance between adjacent nodes?
Answer: D (0.75cm)
λ = v/f = 60 ÷ 40 = 1.5 cm. Adjacent nodes are half a wavelength apart: 0.75 cm.
Calculate the height of the image formed by a pinhole camera of length 12cm used to photograph an object 60cm away from the hole and 70cm high
Answer: D (14cm)
Image height ÷ object height = image distance ÷ object distance, so h = 70 × 12 ÷ 60 = 14 cm.
Which of the following is a scalar quantity
Answer: D (Mass)
Mass has size only. Tension, weight and impulse all have direction, so they are vectors.