Question 1

Which scientist is credited with the discovery of the law of gravitation?

Accepted Answer

Sir Isaac Newton formulated the law of universal gravitation in 1687, which states that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Question 2

What is the SI unit of force?

Accepted Answer

The Newton (N) is the SI unit of force, named after Sir Isaac Newton. One Newton is defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second squared (F = ma).

Question 3

What is the SI unit of temperature?

Accepted Answer

The Kelvin (K) is the SI unit of temperature. It is an absolute temperature scale where 0 K represents absolute zero (the lowest possible temperature). The Celsius scale is commonly used but is not the SI unit.

Question 4

Which of the following is an example of a scalar quantity?

Accepted Answer

A scalar quantity has only magnitude and no direction. Speed is a scalar quantity (e.g., 60 km/h), whereas velocity is a vector quantity because it includes both magnitude and direction (e.g., 60 km/h north).

Question 5

Which of the following is the SI unit of electric current?

Accepted Answer

The SI unit of electric current is the Ampere (A), named after French physicist André-Marie Ampère. It is defined as the flow of one coulomb of charge per second.

Question 6

Which of the following correctly describes the relationship between work, energy, and power?

Accepted Answer

Work is the transfer of energy by a force acting over a distance (W = F·d). Energy is the capacity to do work. Power is the rate at which work is done or energy is transferred (P = W/t). All three are related: power measures how quickly work is performed.

Question 7

What is the relationship between velocity and speed in physics?

Accepted Answer

Speed is a scalar quantity (magnitude only) representing the rate of distance covered, while velocity is a vector quantity (magnitude and direction) representing the rate of displacement. Velocity can be zero while speed is not, and they are equal only when motion is in a straight line without change in direction.

Question 8

Which of the following statements about friction is correct?

Accepted Answer

Friction is a force that opposes relative motion between two surfaces in contact. Static friction prevents motion from starting, while kinetic friction acts on objects already in motion. Friction always acts opposite to the direction of motion or attempted motion.

Question 9

An object of mass 2 kg is lifted vertically upward by a distance of 5 m against gravity (g = 10 m/s²). How much work is done against gravity, and what is the gravitational potential energy gained by the object?

Accepted Answer

Work done against gravity: W = mgh = 2 × 10 × 5 = 100 J. Gravitational potential energy gained: ΔPE = mgh = 2 × 10 × 5 = 100 J. Both are equal because all work done against gravity is converted to potential energy.

Question 10

A ball is thrown vertically upward from the ground with an initial velocity of 20 m/s. Neglecting air resistance and taking g = 10 m/s², what is the maximum height reached by the ball, and at what time does it reach this height?

Accepted Answer

Using kinematic equations: v² = u² - 2gh. At maximum height, v = 0. Therefore, 0 = (20)² - 2(10)h → h = 20 m. Time to reach maximum height: v = u - gt → 0 = 20 - 10t → t = 2 seconds.

Question 11

A 5 kg object is placed on a horizontal frictionless surface. A horizontal force of 25 N is applied to it. What is the acceleration of the object, and what is the net force acting on it?

Accepted Answer

Using Newton's Second Law: F = ma. Net force = Applied force = 25 N (no friction). Acceleration a = F/m = 25/5 = 5 m/s². The net force is the applied force itself since there is no friction or opposing force.

Question 12

A light ray travels from air (refractive index = 1) into glass (refractive index = 1.5) at an angle of incidence of 30°. Using Snell's Law (n₁ sin θ₁ = n₂ sin θ₂), what is the angle of refraction in the glass?

Accepted Answer

Applying Snell's Law: n₁ sin θ₁ = n₂ sin θ₂ → 1 × sin(30°) = 1.5 × sin(θ₂) → 1 × 0.5 = 1.5 × sin(θ₂) → sin(θ₂) = 0.5/1.5 = 1/3 ≈ 0.333 → θ₂ = arcsin(0.333) ≈ 19.47° ≈ 19.5° or approximately 19°-20°.

Question 13

A sound wave has a frequency of 440 Hz and travels through air at a speed of 330 m/s. What is the wavelength of this sound wave?

Accepted Answer

Using the wave equation: v = f × λ, where v is velocity, f is frequency, and λ is wavelength. Rearranging: λ = v/f = 330/440 = 0.75 m = 75 cm.

Question 14

A student observes that when a metal rod is heated at one end, the heat gradually reaches the other end. Which of the following best explains this phenomenon and identifies the primary mode of heat transfer in solids?

Accepted Answer

In solids, heat is primarily transferred through conduction. When a metal rod is heated at one end, the atoms at that end vibrate more vigorously due to increased thermal energy. These vibrating atoms collide with neighboring atoms, transferring kinetic energy to them. This process continues along the length of the rod without any bulk movement of the material itself. Metals are excellent conductors of heat because they contain free electrons that can also carry thermal energy rapidly through the material. This is distinct from convection (which requires fluid movement) and radiation (which requires no medium).

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