Physics 2025 Jamb Examination

Reverberation is the persistence of sound in a space after the source has stopped, caused by multiple reflections. Perforated and soft materials are good absorbers of sound; they trap sound waves and convert their energy into heat instead of reflecting them back into the room. This effectively reduces reverberation time and improves sound clarity in large halls.

An object sinks when its weight is greater than the maximum upthrust (buoyant force) provided by the liquid. Since upthrust is the weight of the fluid displaced, an object whose density is greater than water will weigh more than the volume of water it displaces, causing it to sink to the bottom.

Temperature gradient is the change in temperature per unit length. \[ \text{Temperature Gradient} = \frac{T_2 - T_1}{L} \] \[ 416 = \frac{\Delta T}{0.2} \] \[ \Delta T = 416 \times 0.2 = 83.2 \text{ K} \text{ (or } ^\circ\text{C)} \] If one end is 233ºC, the other end (depending on the direction of heat flow) could be higher or lower. Looking at the options, we subtract the difference: \[ 233 - 83.2 = 149.8 \text{ or } 233 + 83.2 = 316.2 \text{ (rounding/variation might apply)} \]. Checking standard JAMB phrasing, it usually implies the drop in temperature: \( 233 + (416 \times 0.2) = 316.2 \).

Brownian motion is the random, erratic movement of microscopic particles suspended in a fluid (liquid or gas) resulting from their collision with the fast-moving molecules of the fluid. This provides strong evidence for the kinetic theory of matter.

Using Faraday's first law: \( m = zIt \). The electrochemical equivalent (z) for Silver is approximately \( 0.001118 \text{ g/C} \). \[ I = 0.8 \text{ A} \] \[ t = 25 \times 60 = 1500 \text{ seconds} \] \[ m = 0.001118 \times 0.8 \times 1500 \] \[ m = 0.001118 \times 1200 \approx 1.3416 \text{ g} \]

Thermal capacity (or heat capacity) is the amount of heat required to raise the temperature of a whole body by 1 K. It is calculated as the product of the mass of the body and the specific heat capacity of the material it is made of (\( C = mc \)). Therefore, it depends on both the amount of matter (mass) and the type of substance (nature).

We use the ideal gas equation: \( PV = nRT \). First, convert temperature to Kelvin: \( T = 17 + 273 = 290 \, \text{K} \). Given: \( V = 4.5 \, \text{m}^3 \), \( n = 8.3 \, \text{moles} \), \( R = 8.31 \, \text{JK}^{-1}\text{mol}^{-1} \). \[ P = \frac{nRT}{V} = \frac{8.3 \times 8.31 \times 290}{4.5} \] \[ P = \frac{19998.77}{4.5} \approx 4444.17 \, \text{Pa} \]

Frictional force is the force that resists the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. It acts tangentially to the surface of contact and always in a direction opposite to the intended or actual motion.

A neutral point in a magnetic field is a point where the magnetic field produced by a magnet is exactly equal in magnitude and opposite in direction to the Earth's horizontal magnetic field. At this specific location, the resultant magnetic field strength is zero, and a compass needle will not point in any specific direction.

Specific gravity (or relative density) is the ratio of the density of a substance to the density of water. \[ \text{Specific Gravity} = \frac{\text{Density of liquid}}{\text{Density of water}} \] \[ 0.76 = \frac{\text{Density of liquid}}{1000} \] \[ \text{Density of liquid} = 0.76 \times 1000 = 760 \, \text{kgm}^{-3} \]