Railway Science (Physics-Force and Pressure) (Part-II)

Total Questions: 50

41. In which of the following is the value of inertia maximum ? [RRB Group D 16/10/2018 (Morning)]

Correct Answer: (d) Trains and Airplanes
Solution:

The moment of inertia of a rigid body depends on the mass of the body, its shape and size; distribution of mass about the axis of rotation, and the position and orientation of the axis of rotation. The dimensions of moments of inertia [ML²] and its SI units are kg m² .

42. If an object is pulled by holding it from both ends, then the force applied on it is called _______ [RRB Group D 16/10/2018 (Morning)]

Correct Answer: (d) Tension
Solution:

It refers to the force transmitted when a rope, wire, cable or string is tethered by forces acting on opposite ends. It is given by the formula: T= mg, where T is tension, m is mass (kg) and g is acceleration due to gravity (9.8 m/sec²).

43. An object moves with a constant speed when the value of _______ is negligible. [RRB Group D 16/10/2018 (Morning)]

Correct Answer: (c) force
Solution:

According to Newton's first law of motion, an object will remain at rest or move in a straight line with constant speed (which includes moving at a constant velocity) if the net force acting on it is zero. When the value of force is negligible, it means that the net force acting on the object is close to zero.

44. Which of the following statements is incorrect? [RRB Group D 16/10/2018 (Afternoon)]

Correct Answer: (d) Action and reaction forces act on the same body.
Solution:

Newton's Third Law of Motion: This law states that for every action force, there is an equal and opposite reaction force. These forces always act on different bodies. Examples: Kicking a ball (action). When a rocket releases exhaust gasses, the force pushing the exhaust out (action) is met by an equal and opposite force propelling the rocket forward (reaction).

45. The distance covered by an object in unit time is called _______. [RRB Group D 16/10/2018 (Afternoon)]

Correct Answer: (d) average speed
Solution:

Distance is the total length of the path traveled, without considering direction, making it a scalar quantity with only magnitude. Average velocity is found by dividing displacement by total time, considering direction. Displacement refers to the shortest distance between the object's initial and final positions during its motion.

46. Motion of a body with constant speed in a circular path is called: [RRB Group D 16/10/2018 (Evening)]

Correct Answer: (a) Uniform circular motion
Solution:

Non-uniform circular motion: This describes a situation where the body's speed changes as it moves along the circular path. Circulatory motion: This is a broader term that can encompass both uniform and non-uniform circular motion, as well as other types of closed-loop movements (e.g., elliptical).

47. The forces between two bodies are always: [RRB Group D 16/10/2018 (Evening)]

Correct Answer: (b) equal and in the opposite direction
Solution:

Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. In simple terms, whenever one object exerts a force on another object, the second object always exerts a force back on the first object that is equal in strength but opposite in direction.

48. A graph showing velocity of an object with time is known as : [RRB Group D 22/10/2018 (Morning)]

Correct Answer: (c) velocity - time graph
Solution:

The slope of a velocity graph represents the acceleration of the object. The area under a velocity graph represents the displacement of the object.

49. Which of the following equations establishes the relationship between position and velocity ? [RRB Group D 23/10/2018 (Evening)]

Correct Answer: (b) 2as = v² - u²
Solution:

Other Equations of Motion : 𝑣 = 𝑢 + 𝑎𝑡 (velocity and time). 𝑠 = 𝑢𝑡 + 1/2 𝑎𝑡²  (Position and time). Physical Quantity and Formula : Charge (Q, Columb) = I.t. Voltage (V, Volt) = IR, Speed (m/s) = Distance/Time, Velocity (m/s) = Displacement/time, Acceleration (m/𝑠²)  = Change in Velocity/Change in time, Force (Newton) = mass × acceleration, Kinetic Energy (Joule) = 1/2 𝑚𝑣²  , Potential Energy (Joule) = mgh, Power (watt) = VI = 𝑖²R = 𝑉²/R .

50. The motion of a bus on a crowded road is an example of _____ motion. [RRB Group D 24/10/2018 (Morning)]

Correct Answer: (a) non-uniform
Solution:

It moves with a variable speed in equal time intervals at different distances. For example; a bike travels in traffic. The velocity of non-uniform motion changes with time. Uniform Motion - When it moves with a constant or uniform speed at a certain distance in an equal time interval. For example; Airplanes fly at a constant speed in the air. Examples of circular motion - Moon orbiting around the Earth or the Earth revolving around the Sun. Linear motion example - Moving of a train in straight rail-tracks.