JEE · Physics · Kinematics doubts
15 doubts found
What does “Instantaneous velocity” actually mean in Kinematics, and why does it matter for JEE?
the velocity at a single instant — the slope of the position–time graph at that point.
I keep getting “Instantaneous velocity” questions wrong in Kinematics. What's the trap?
confusing average velocity (total displacement/total time) with instantaneous velocity.
What does “Acceleration” actually mean in Kinematics, and why does it matter for JEE?
the rate of change of velocity; it is a vector, so direction matters.
I keep getting “Acceleration” questions wrong in Kinematics. What's the trap?
assuming acceleration is zero whenever velocity is zero (e.g. at the top of a throw, v=0 but a=−g).
What does “Equations of motion” actually mean in Kinematics, and why does it matter for JEE?
the v=u+at family that connects u, v, a, s and t — valid only for constant acceleration.
I keep getting “Equations of motion” questions wrong in Kinematics. What's the trap?
using them when acceleration is changing.
What does “Projectile motion” actually mean in Kinematics, and why does it matter for JEE?
motion under gravity where horizontal and vertical motions are independent — horizontal a=0, vertical a=−g.
I keep getting “Projectile motion” questions wrong in Kinematics. What's the trap?
applying v=u+at to the whole velocity instead of resolving into x and y components.
What does “Relative velocity” actually mean in Kinematics, and why does it matter for JEE?
the velocity of A as seen from B equals vector v(A) − v(B).
I keep getting “Relative velocity” questions wrong in Kinematics. What's the trap?
adding speeds as plain numbers instead of subtracting vectors.
What is the difference between distance and displacement?
Distance is the total path length (scalar, never decreases); displacement is the straight-line vector from start to finish (can be zero on a round trip).
What is the difference between speed and velocity?
Speed is a scalar (how fast); velocity is a vector (how fast AND in which direction).
What is the difference between average velocity and instantaneous velocity?
Average velocity is displacement over a time interval; instantaneous velocity is the value at one exact moment.
When do I use v = u + at in Kinematics, and what does it mean?
final velocity after time t under constant acceleration.
When do I use s = ut + ½at² in Kinematics, and what does it mean?
displacement after time t under constant acceleration.