Question 1

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

Accepted Answer

The SI unit of electric current is Ampere (A), named after French physicist André-Marie Ampère. It measures the flow of electric charge through a conductor. Volt is the unit of potential difference, Ohm is the unit of resistance, and Watt is the unit of power.

Question 2

A 2 kg object is pushed with a force of 10 N on a frictionless surface. What is the acceleration of the object?

Accepted Answer

Using Newton's second law of motion, F = ma, where F = 10 N and m = 2 kg. Solving for acceleration: a = F/m = 10/2 = 5 m/s². Therefore, the answer is C.

Question 3

A person standing on the ground experiences a normal force. This normal force is an example of which type of force?

Accepted Answer

The normal force experienced by a person standing on the ground is a contact force. Contact forces arise from physical contact between two objects. The ground exerts an upward normal force perpendicular to its surface on the person, balancing the gravitational force acting downward. This is distinct from non-contact forces like gravity, magnetism, and electrostatic forces.

Question 4

When a ball is thrown vertically upward and returns to the same height, what is the net displacement of the ball?

Accepted Answer

Displacement is defined as the change in position from the initial point to the final point, measured in a straight line. When a ball is thrown vertically upward and returns to the same height from which it was thrown, the initial and final positions are identical. Therefore, the net displacement is zero, regardless of the distance traveled (which would be non-zero).

Question 5

A person pushes a heavy box across a rough floor at constant velocity. Which statement correctly describes the net force acting on the box?

Accepted Answer

According to Newton's First Law of Motion, an object moving at constant velocity has zero acceleration. By Newton's Second Law (F_net = ma), if acceleration is zero, then the net force must be zero. This means the applied force pushing the box is balanced by the friction force opposing the motion. The box is in equilibrium, even though it is moving.

Question 6

Which of the following correctly describes the relationship between mass and inertia?

Accepted Answer

Inertia is the property of matter that resists changes in motion. Mass is the quantitative measure of inertia. An object with greater mass has greater inertia and requires a larger force to change its velocity. This relationship is fundamental to Newton's Second Law (F = ma), where mass is the measure of an object's resistance to acceleration.

Question 7

A ball is thrown vertically upward with an initial velocity of 20 m/s. Assuming g = 10 m/s², what is the maximum height reached by the ball?

Accepted Answer

Using the kinematic equation v² = u² - 2gh, where final velocity v = 0 at maximum height, initial velocity u = 20 m/s, and g = 10 m/s². Solving: 0 = (20)² - 2(10)h → 0 = 400 - 20h → h = 20 m. Therefore, the answer is B.

Question 8

Which of the following is the SI unit of force?

Accepted Answer

The SI unit of force is the Newton (N), named after Sir Isaac Newton. One Newton is defined as the force required to accelerate a mass of 1 kilogram at a rate of 1 meter per second squared (1 N = 1 kg·m/s²). Therefore, the answer is C.

Question 9

A car traveling at 72 km/h applies brakes and comes to rest in 5 seconds. What is the magnitude of deceleration?

Accepted Answer

First, convert 72 km/h to m/s: 72 × (5/18) = 20 m/s. Using the equation v = u - at (negative because it's deceleration), where final velocity v = 0, initial velocity u = 20 m/s, and time t = 5 s: 0 = 20 - a(5) → a = 4 m/s². Therefore, the answer is B.

Question 10

What is the SI unit of pressure?

Accepted Answer

The SI unit of pressure is the Pascal (Pa), named after Blaise Pascal. One Pascal is defined as one Newton per square meter (1 Pa = 1 N/m²). Therefore, the answer is D.

Question 11

A spring with spring constant k = 100 N/m is compressed by 0.2 m. What is the elastic potential energy stored in the spring?

Accepted Answer

The elastic potential energy in a spring is given by E = ½kx², where k = 100 N/m and x = 0.2 m: E = ½ × 100 × (0.2)² = ½ × 100 × 0.04 = 2 J. Therefore, answer is B.

Question 12

A sound wave travels through air at a speed of 340 m/s. If the frequency of the sound is 170 Hz, what is the wavelength of the sound wave?

Accepted Answer

The relationship between wave speed, frequency, and wavelength is v = fλ, where v = 340 m/s and f = 170 Hz: λ = v/f = 340/170 = 2 m. Therefore, answer is D.

Question 13

A student observes that when a steel ball is dropped from a height of 20 meters, it takes 2 seconds to reach the ground. Ignoring air resistance, what is the approximate value of acceleration due to gravity at that location?

Accepted Answer

Using the kinematic equation s = ut + (1/2)gt², where s = 20 m, u = 0 (dropped, not thrown), and t = 2 s: 20 = 0 + (1/2)g(2)² → 20 = 2g → g = 10 m/s². This is the standard value of acceleration due to gravity used in Indian physics curricula. Therefore, the answer is B.

Question 14

A 5 kg object is pushed horizontally on a frictionless surface with a force of 20 N. What is the acceleration of the object?

Accepted Answer

Using Newton's Second Law of Motion, F = ma, where F = 20 N and m = 5 kg: a = F/m = 20/5 = 4 m/s². This is a direct application of the fundamental equation of classical mechanics. Therefore, the answer is C.

Question 15

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

Accepted Answer

Snell's Law states: n₁ sin(θ₁) = n₂ sin(θ₂). Here, n₁ = 1 (air), θ₁ = 30°, n₂ = 1.5 (glass), and θ₂ is unknown. Substituting: 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°, which rounds to approximately 19.5° or 20°. Therefore, the answer is B.

Question 16

A 2 kg block is lifted vertically upward at constant velocity. What is the tension in the rope holding the block? (Use g = 10 m/s²)

Accepted Answer

When an object moves at constant velocity, its acceleration is zero, meaning the net force is zero (Newton's First Law). The forces acting on the block are tension (T) upward and weight (W = mg) downward. For equilibrium: T = W = mg = 2 × 10 = 20 N. Therefore, the answer is A.

Question 17

A car traveling at 20 m/s brakes uniformly and comes to rest in 4 seconds. What is the magnitude of deceleration?

Accepted Answer

Using the kinematic equation v = u + at, where v = 0 m/s (final velocity), u = 20 m/s (initial velocity), and t = 4 s: 0 = 20 + a(4) → a = -20/4 = -5 m/s². The magnitude of deceleration is |a| = 5 m/s². Therefore, the answer is D.

Question 18

A steel ball is dropped from a height of 80 meters above the ground. Neglecting air resistance and taking g = 10 m/s², what is the velocity of the ball just before it hits the ground?

Accepted Answer

Using the kinematic equation v² = u² + 2as, where u = 0 (dropped from rest), a = g = 10 m/s², and s = 80 m: v² = 0 + 2(10)(80) = 1600, so v = 40 m/s. Therefore, answer is B.

Question 19

A 5 kg object is placed on a frictionless horizontal surface and pushed with a force of 20 N. What is the acceleration of the object?

Accepted Answer

Using Newton's Second Law, F = ma, where F = 20 N and m = 5 kg: a = F/m = 20/5 = 4 m/s². Therefore, answer is C.

Question 20

A light ray travels from air (refractive index = 1.0) into glass (refractive index = 1.5) at an angle of incidence of 30°. Using Snell's Law, what is the angle of refraction in the glass?

Accepted Answer

Snell's Law states n₁ sin θ₁ = n₂ sin θ₂. Here, 1.0 × sin(30°) = 1.5 × sin(θ₂), so 1.0 × 0.5 = 1.5 × sin(θ₂), giving sin(θ₂) = 0.5/1.5 = 1/3 ≈ 0.333, so θ₂ ≈ 19.5° (approximately 19-20°). Therefore, answer is A.

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