Physics : PYQs with Answers

Momentum $p = mv = 5 \times 4 = 20$ kg·m/s.

Velocity and force are vector quantities (have both magnitude and direction). Speed and temperature are scalar quantities.

In forward bias, the external voltage reduces the potential barrier, allowing significant current to flow through the diode.

Current through 4 Ω: $I_1 = 12/4 = 3$ A. Current through 6 Ω: $I_2 = 12/6 = 2$ A. Total: $I = 3 + 2 = 5$ A.

$R = \frac{u^2 \sin 2\theta}{g} = \frac{20^2 \times \sin 60°}{10} = \frac{400 \times \frac{\sqrt{3}}{2}}{10} = 20\sqrt{3}$ m.

Total internal reflection occurs when light passes from a denser to a rarer medium at an angle equal to or greater than the critical angle. It is the principle behind optical fibres.

Electric motors work on the principle that a current-carrying conductor placed in a magnetic field experiences a force (Fleming's left-hand rule).

The speed of sound in air at 0°C is approximately 331 m/s. It increases with temperature.

Radiation transfers heat through electromagnetic waves and does not need any medium, unlike conduction and convection.

$g = GM/R^2$. If R doubles, $g$ becomes $GM/(2R)^2 = g/4$. So g becomes one-fourth.

Power $P = VI = 220 \times 0.5 = 110$ W.

Static friction acts on a body at rest when an external force is applied but motion has not started. It opposes the tendency of motion.

When light travels from denser to rarer medium, the refracted ray bends away from the normal because speed increases. This follows Snell's law: $n_1 \sin\theta_1 = n_2 \sin\theta_2$.