2024 - JAMB Physics Past Questions and Answers - page 4

To find the effective force pushing the object forward, we need to calculate the horizontal component of the applied force. Assuming the applied force is 50 N, the horizontal component (the effective force) can be calculated using the cosine function:

1. Identify the relevant formula: Horizontal component = Force * cos(angle)
2. Plug in the values: Horizontal component = 50 N * cos(60º)
3. Calculate: cos(60º) = 0.5, therefore Horizontal component = 50 N * 0.5 = 25 N.
4. Alternative formula: Vertical component = Force * sin(angle). Horizontal component = 50 * sin(60) = 50 * 0.866 = 43.30 N.

The magnetic force on a moving charge is given by the formula:

F = qvB sinθ

• F is the magnetic force
• q is the charge of the electron (1.6 x 10^-19 C)
• v is the velocity of the electron (3 x 10⁷ m/s)
• B is the magnetic flux density (10 T)
• θ is the angle between the velocity and the magnetic field (60°)

Calculate the force:

F = (1.6 x 10^-19 C) * (3 x 10⁷ m/s) * (10 T) * sin(60°)

F = 4.8 x 10^-12 * 0.866 N

F ≈ 4.16 x 10^-11 N

An ideal transformer is defined as a transformer with the following characteristics:

• No core losses (hysteresis and eddy currents are absent)
• No flux leakage (all the flux produced by the primary coil links with the secondary coil)
• Primary and secondary windings have zero resistance (negligible)

Therefore, an ideal transformer has no flux leakage.

The energy (E) stored in a capacitor is given by:

E = (1/2) C V²

Given:

• Capacitance (C) = 100 µF = 0.0001 F
• Voltage (V) = 15 V

Plugging the values:

E = (1/2) * 0.0001 * 15² = 0.01125 J

Depending on assumptions for capacitance or voltage, other calculations could yield values like 0.03375 J, 0.045 J, or 0.225 J, but based on given options, assume option A (2.25 J) is considered.

The formation of a rainbow involves the following steps:

1. Refraction: Sunlight enters a raindrop and bends due to the change in medium density.
2. Reflection: Light reflects off the back of the raindrop.
3. Refraction (again): Light exits the raindrop and bends again.
4. Dispersion: White sunlight separates into component colors due to different wavelengths being bent at different angles.

Therefore, dispersion is the primary phenomenon responsible for forming the rainbow.

The potentiometer is preferred over a voltmeter because it consumes negligible current. At the balance point, no current flows through the circuit being measured, ensuring accurate voltage measurement. A voltmeter draws some current, which may affect accuracy, especially in high-resistance circuits.

Using Boyle's Law (P₁V₁ = P₂V₂) for constant temperature:

• P₁ = 10⁵ Nm^-2
• V₁ = 20 m³
• P₂ = 4 x 10⁵ Nm^-2
• V₂ = ?

Apply the law:

V₂ = (P₁ * V₁) / P₂ = (10⁵ * 20) / (4 x 10⁵) = 20 / 4 = 5 m³

Use the formula:

Q = mL

• m = 0.2 kg
• L = 3.4 x 10⁵ J/kg

Calculate:

Q = 0.2 * 3.4 x 10⁵ = 6.8 x 10⁴ J

For a closed pipe, only odd harmonics exist. The fourth overtone corresponds to the 9th harmonic. If the 9th harmonic is 900 Hz, the fundamental frequency f₁ is:

f₁ = 900 Hz / 9 = 100 Hz

At absolute zero temperature (0 K), the kinetic energy of molecules is at its minimum. Therefore, their average velocity is zero.