Physics in Depth

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Relative velocity Relative velocity, \(\vec{v_{AB}}\), is the velocity of an object A in the rest frame of an object B. Rest frame of a particle is the coordinate system (frame of reference) in which the particle is at rest . It can be simply defined as, the velocity of an object with respect to another object . Suppose you are in a car A moving north at 90 km/h (with respect to the object in the ground outside). To another man in a car B moving towards north with same speed, you seem to be stationary. Let's discuss this in more detail. For this, we consider following three cases: When the two bodies, body A and body B, are moving in the same direction with velocity \(\vec{v_A}\) and \(\vec{v_B}\) respectively, then the relative velocity of A with respect to B is, \[\vec{v_{AB}}=\vec{v_A}-\vec{v_B}\] So, in above example, it must be clear that for a person in car B moving alongside you with the same speed as yours, you are at rest. When this bodies ar...

Kinematics Rest and Motion When do you declare that some body is in rest or in motion ? Place the book on a table and watch it! Is it in rest? Imagine you being on moon and by some means you could watch your book on your table. Would you again see it in rest? In first case, you would see that the book is in rest but when you are on moon you would see the table, the book and the Earth as a whole in a motion. You are correct in both the cases and it's a good news. Hurray! .It is because rest and motion are not absolute terms but are relative . The book is in rest when you see it from your room because you and the book both do not change position with respect to each other, but it is in motion when you see it from the moon because the moon is moving with respect to the book and book moves with respect to the moon. So, let's set up a definition. If a body changes it's position with respect to the observer ( or reference frame ), then it is said t...

Scalars and Vectors Vector Multiplication Multiplication of a vector by a scalar Let \(\vec{a}\) be the vector and \(\vec{k}\) be the scalar, if we multipy them the result is a vector (i.e., k\(\vec{a}\)). Multiplication of a vector by a vector Vector multiplication are not straightforward as scalar multiplication as they do not follow the ordinary rules of algebra. We can multiply any two vectors in two ways: a. Scalar product and b. Vector product Scalar product / dot product Consider any two vectors \(\vec{a}\) and \(\vec{b}\) inclined at an angle \(\theta\) with each other as in fig. Then we define the scalar product of these two vectors as, \(\vec{a} . \vec{b} = ab cos\theta \) Note that! \(\vec{a} . \vec{b} = \vec{b} . \vec{a}\) Scalar product of any two vectors is always scalar quantity. For example, \(P = \vec{F} . \vec{v}\). Here, force and velocity are vector quantity but the power which is a scalar product of force and velocity is ...

Physical quantities ( measurable quantities ) on the basis of whether they represent magnitude or both magnitude and direction; are broadly classified as scalars and vectors. What are scalars? Scalars are quantities which have magnitude but no direction. A car moving on a road at 80 km/h is said to have a speed of 80 km/h. Speed is a quantity which has no direction but only magnitude, like mass or density or temperature . These quantities are thus the examples of scalars. What are vectors? Vectors are quantities which have both magnitude and direction. A car moving on a road at 80 km/h in north-east direction is said to have a velocity of 80 km/h NE (i.e., north-east ). Velocity is a quantity which has both magnitude and direction, like displacement or force or acceleration . These quantities are thus the examples of vectors. Let's point some of the differences between scalars and vectors. Addition : Scalars obey the ordinary ...

NEB Short Question Tips — Class 11 & 12 NEB · Class 11 & 12 · Science Crack the short questions Seven exam-day strategies — with real examples from Physics — that separate full-marks answers from half-marks ones. Core strategies 🧘 Don't panic Most students freeze the moment they read the question. That's normal — and it passes. Just calmly remember the concepts you've studied so far. Physics rule of thumb Panic time ∝ 1 / Preparation. The more you've practiced, the quieter that first-glance fear gets. 🔍 Read the question carefully — twice Short questions are built on precise language. Underline key words before writing anything. The difference between "can" and "must", or "speed" and "velocity", is often the en...

Physics is the mathematical formulation of the natural laws. To describe the laws of nature, we need the quantitative description that involves measurement and comparison of physical quantities. To measure a physical quantity we need some standard unit of that quantity. We measure each physical quantity in its own units, by comparison with a standard . The unit is a unique name that we assign to measure of that quantity - for example, meter (m) for the quantity length. The standard corresponds to 1.0 unit of the quantity. The dimension of a physical quantity is defined as the power to which the fundamental quantities are raised to express the physical quantity. [M], [L], [T], [A], etc. are the respective dimensions of mass, length, time and current. Homogeneity of dimensions in an equation : The dimensions of all term in an equation must be identical.i.e. dimension in L.H.S. of an equation is equal to the dimension in R.H.S. of an equation. Limitation of the...

Hey everyone! Let's cut past the usual cliché advice. If you want to systematically build real confidence and ace your upcoming board exams, integrate these four practical habits into your daily routine. 1. Time Management: Break the "Wall Chart" Cycle We've all done it: spent hours designing a beautiful color-coded study routine, pasted it to the wall, followed it perfectly for three days, and then completely abandoned it. Wall charts don't clear exams; mental determination does. Try this instead: Keep your routine flexible but non-negotiable. If your concentration dips during the day, take a quick 15-to-20-minute power nap to reset your brain. Crucially, before you close your eyes at night, do a 5-minute mental recap. Close your eyes and silently map out the core concepts you studied that day—if you can recall it smoothly in the dark, it's locked into your long-term memory. 2. Premium Fuel for Yo...