Nature of Physics

Motion in Plane: Previously we discussed motion in a straight line. Motion in straight line belongs to one dimension. Thus, Motion in plane defined in two dimensions. If an object is free to move in a plane, its position can be located with two co-ordinates. Let's consider an object is situated in x-y plane. It moves along the following path- During the path object moves along X direction as well as Y direction. In time interval t to t+t 1  (here t 1  is very small time interval) object displaced x 1  and y 1  in X and Y direction  respectively . Displacement is in both X and Y direction, so there will be different velocity and acceleration in both directions. If we take u x  ,v x  ,a x  as initial velocity ,final velocity and acceleration in X direction and  u y  ,v y  ,a y  as initial velocity ,final velocity and acceleration in Y direction. Consider both the accelerations constant. In time t object have 'x' and 'y' displacements along X-axes and Y-axes respective

Motion in Straight Line: Motion in straight line is defined as motion in one dimension (1-D). It is also known as linear motion. It can be participated in two parts - (i) uniform linear motion and  (ii) non-uniform linear motion Uniform Linear Motion: In this motion a body covers equal distance in equal time intervals i.e. velocity along the path is constant.  In this motion a body moves with a constant acceleration.  Non-uniform Linear Motion: In this motion a body moves with a variable velocity in a given interval of time. Equation of Motion with constant Acceleration: Consider that a particle has constant acceleration 'a'. It's initial velocity is 'u' and final velocity is 'v' after 't' time. Now acceleration can be written as: dv/dt = a    Particle covers 's' distance or displacement (since particle is moving along the straight line) in time 't'. From 1st equation- write equation 1st again- Displacement of Particle in nth second:

Rest and Motion: We can say if a body does not change it's position with time, it is at rest. And if a body changes it's position with time, it is said to be moving. But, how do we know that a particle is in motion or not ? To find the position of the particle we need a frame of reference. Let's fix the frame of reference as the three mutually perpendicular axes X, Y and Z. Assume that particle has co-ordinates (x, y, z) at any instant. After a while, if all co-ordinates of the particle remains same with time that means particle is at rest with respect to that frame of reference. And if one or more co-ordinates change with time, it is called as moving particle. There is not any restriction of a choice of a frame of reference. We can choose a frame of reference according to our convenience.  For simplicity assume yourself at rest at the frame of reference. For example a bus is moving with a speed. First, I take bus as the reference that means I should have put m

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Vector Addition:   C onsider that a man is walking on a path ABC (from A to B and then from B to C) as shown in the figure. In this case displacement AC vector can be written as the sum of the AB vector and BC vector.                                 AB + BC = AC                    this is known as the  triangle rule   of   vectors.                                     So, in the general case if we have two vectors a and b are positioned so that the initial point of one coincides with the terminal point of the other. Then, vector (a+b) represented by the third side c vector of the triangle, which is the addition of (a+b) vector  or we can say resultant vector of a vector and b vector.                                          a + b = c    If we rotate b vector from π angle without changing its magnitude then according to figure in triangle ∆ABC'                                            a + (-b) = c'                                            a - b = c'  

PHYSICAL QUANTITY: SCALAR and VECTOR A  physical quantity  is a property of a material or system that can  be quantified by  measurement. A physical quantity can be expressed as the combination of a magnitude and a  unit. Ex: 5 kg in this ‘5’ is magnitude and ‘kg’ is unit. Physical quantity can be operated in two parts:             (i) Scalar Quantity               (ii) Vector Quantity Scalars: •   A physical quantity which has only magnitude. •  They do not have any direction.   ex: time, mass, speed, distance, volume, energy, work, temperature, electric charge.   Vectors: •  A vector quantity is defined as the physical quantity that has both, magnitude as well as direction. ex: displacement, force, torque, momentum, acceleration, velocity, etc. Representation of Vector: A vector is represented as a directed line segment.                   this vector can be represented as AB 乛   or  ā .                 Magnitude of this vecto