Physics (Part-I) (UPSC)

An object on an inclined plane with inclination → moves with an acceleration g sinθ down the plane. The time taken to reach the bottom is given by

The velocity after time is given by
v = u + gt
Here,
u = 0  t = 2s g = 9.8m / (s²)
v = 0 + (9.8 × 2) = 19.6m / s
According to the velocity meaning, it can be defined as the rate of change of the object's position with respect to a frame of reference and time. It might sound complicated, but velocity is basically speeding in a specific direction. It is a vector quantity, which means we need both magnitude (speed) and direction to define velocity. The SI unit of it is metre per second (m/s). If there is a change in magnitude or the direction of the velocity of a body, then it is said to be accelerating.
Initial velocity describes how fast an object travels when gravity first applies force on the object. On the other hand, the final velocity is a vector quantity that measures the speed and direction of a moving body after it has reached its maximum acceleration.

When the hunter fires the bullet, both the bullet and the monkey experience the same gravitational acceleration downwards. As the bullet travels forward, it also falls towards the ground, just like the monkey after jumping off the branch. Since the initial aim was at the monkey's eyebrows, both the monkey and the bullet fall the same vertical distance due to gravity during the bullet's flight time. Thus, the bullet hits the monkey as aimed, demonstrating the independence of horizontal and vertical motion under gravity.

Rising of underground water is primarily driven by pressure differences and permeability of soil and rock layers, rather than capillarity. Therefore, the rising of underground water is not primarily caused by capillarity but rather by hydrostatic pressure and other geological factors.
We can define capillary action as a phenomenon where the ascension of liquids through a tube or cylinder takes place. This primarily occurs due to adhesive and cohesive forces.
The liquid is drawn upward due to this interaction between the phenomena. The narrower the tube, the higher will the liquid rise. If any of the two phenomena, i.e., that of surface tension and a ratio between cohesion to adhesion, increase, the rise will also increase. Although, if the density of the liquid increases, the rise of the liquid in the capillary will lessen.
The amount of water that is held in the capillary also determines the force with which it will rise. The material that surrounds the pores fills the pores and also forms a film over them. The solid materials that are nearest to the molecules of water have the greatest adhesion property. The thickness of the film increases as water is added to the pore, and the magnitude of capillary force gets reduced.
The film that was formed on the outer surface of the soil molecules also may begin to flow. The capillary action is what causes the movement of groundwater through the different zones of soil. How the fluids are transported inside the xylem vessels of plants is also by the capillary action. As the water evaporates from the surface of the leaves, water from the lower levels, that is, the roots, is drawn up by this phenomenon.

A "streamlined" design is one in which objects that move through a gas or liquid are shaped to match these lines, and therefore, reduce the energy required to produce that motion.
Multi point fuel injection system injects fuel into individual cylinders, based on commands from the 'on board engine management system computer-popularly known as the Engine Control Unit/ECU.
These techniques result not only in better 'power balance' amongst the cylinders but also in higher output from each one of them, along with faster throttle response.
The other two options radial tyres and catalytic converter with exhaust do not contribute to make the car more fuel efficient.
The amount of heat produced by the complete combustion of unit mass of a fuel is known as fuel efficiency or calorific value.

First statement can be explained on the basis of laws of motion. First statement involves the use of Newton's third law of motion, "For every action there is an equal and opposite reaction". In first case while whistling a man uses his breathe as a propellant to propel himself. The second statement can be explained on the basis of law of conservation of linear momentum according to which the momentum of body remains conserved until any external force acts upon it.

Mass is a universal constant. The mass of a body remains unchanged in any part of universe. Mass of a body does not change with respect to gravity. It is the weight that changes with gravity.
Mass is a measure of the amount of matter contained in an object. The more mass an object has, the more inertia it possesses. Inertia is the resistance of any physical object to any change in its state of motion. The mass of an object remains the same regardless of its location. Whether the object is on Earth, the Moon, in outer space, or anywhere else in the universe, its mass will not change. This property makes mass a scalar and universal quantity.
Weight is the force exerted on an object due to gravity. It’s the force with which an object is attracted towards a massive body, such as a planet. Particular weight is dependent on both the mass of an object and the acceleration due to gravitation at that location.

The bob of a simple pendulum is attached to a string which pulls the bob along its length.

Here B and C are extreme positions whereas A is mean position. The speed of the bob increases as it approaches the mean position A and continues to move till it reaches C. At C the speed becomes zero. Due to the unbalanced force the bob moves towards the mean position. The speed of the bob is maximum at the mean position and is zero at the extreme positions. Thus, it is clear that in each cycle bob velocity increases from zero to maximum. This means that it attains a given velocity twice. Suppose the bob of the pendulum reaches up to B while oscillating, then AB is the amplitude. For the next oscillation the bob fails to reach B but it will reverse the direction from point B' instead of B. The amplitude of oscillation in the second case is AB' which is less than AB. That means, a retarding force is acting on the bob thereby reducing the amplitude of oscillation. This retarding force is nothing but air-resistance or air-friction. At extreme position, acceleration is maximum. So statement 3 is not correct.

Figure (d) correctly represents the time-distance graph for one dimensional uniform motion.
One dimension implies motion along a straight line or in a single direction. Consider a car or a person driving down a straight road or jogging on a straight track. Think of an object being tossed vertically into the air and then watching it fall. These are examples of one-dimensional motion. There are four main factors to keep track of when evaluating the motion of objects. Time, displacement, velocity, and acceleration are the four variables; time is a scalar quantity, and the other three are vector quantities.

Statement 1 is false. The temperature dependence of liquid viscosity is the phenomenon by which liquid viscosity tends to decrease (or, alternatively, its fluidity tends to increase) as its temperature increases.
Thus, with increase of temperature viscosity of glycerine decrease. Statement 2 is correct because with the rise of temperature in case of liquid, the kinetic energy increases as kinetic energy of liquid molecules is directly proportional to absolute temperature.