2024 - JAMB Physics Past Questions and Answers - page 7

The average translational kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas. This relationship is expressed by the equation: KE = (3/2)kT, where KE is the average kinetic energy, k is Boltzmann's constant, and T is the absolute temperature.

The tangential force opposing the sliding of an object on a surface is the friction force.

Total internal reflection is the phenomenon that occurs when a ray of light strikes a boundary between two media and is completely reflected back into the denser medium. Fiber optics utilizes this principle to transmit light signals over long distances, making it the practical application listed.

Pilots use an aneroid barometer to determine altitude because it's small and convenient. This makes it easy to install and read within an aircraft cockpit. The aneroid barometer measures air pressure, and air pressure decreases with increasing altitude. By knowing the relationship between air pressure and altitude, the pilot can determine the height above sea level.

Here's how to solve the problem:

1. Understand the concepts:

• Velocity Ratio (VR): The ratio of the distance moved by the effort to the distance moved by the load. In this case, VR = 2.
• Mechanical Advantage (MA): The ratio of the load to the effort (MA = Load/Effort).
• Efficiency (η): The ratio of the useful work output to the work input. Efficiency = (MA/VR) * 100%

2. Use the efficiency formula:

• 60% = (MA / 2) * 100%
• 0.6 = MA / 2
• MA = 0.6 * 2 = 1.2

3. Use the Mechanical Advantage formula to find the Effort:

• MA = Load / Effort
• 1.2 = 300N / Effort
• Effort = 300N / 1.2 = 250N

Here's how to solve the problem:

1. Convert power to kW: The refrigerator uses 150W, which is equal to 150/1000 = 0.15 kW.

2. Calculate energy consumption: Energy consumption is calculated using the formula: Energy (kWh) = Power (kW) * Time (hours).

3. Plug in the values: Energy = 0.15 kW * 336 hours = 50.4 kWh.

A vapor is saturated when the rate of condensation equals the rate of evaporation. This signifies a dynamic equilibrium where the number of molecules leaving the liquid phase (evaporation) is equal to the number of molecules returning to the liquid phase (condensation).

Young's modulus (E) is defined as the ratio of tensile stress to tensile strain.

1. Tensile stress is force per unit area, which has dimensions of Force/Area.
    - Force has dimensions of MLT⁻².
    - Area has dimensions of L².
    - Therefore, tensile stress has dimensions of ML⁻¹T⁻².

2. Tensile strain is a dimensionless quantity (change in length/original length).

3. Since Young's modulus is stress/strain, and strain is dimensionless, the dimensions of Young's modulus are the same as the dimensions of stress. Thus, Young's Modulus (E) has the dimensions of ML⁻¹T⁻².

Here's how to solve this problem:

1. Understand the Setup: The diagram shows a galvanometer (a sensitive current-measuring device) being converted into a voltmeter. This is done by connecting a resistor (R) in series with the galvanometer.

2. Relevant Formulas:
- Ohm's Law: V = IR
- When resistors are connected in series, the total resistance is the sum of individual resistances.

3. Given Information: Galvanometer resistance (G) is assumed to be 10 Ω (necessary to solve the problem).

The capacitance of a parallel plate capacitor is given by the formula: C = ε₀ * A / d, where:
- C is the capacitance
- ε₀ is the permittivity of free space (a constant)
- A is the area of the plates
- d is the distance between the plates

From the formula, it is clear that capacitance (C) is inversely proportional to the distance (d) between the plates.