JEE · Physics · Motion in a Plane doubts
9 doubts found
A ball is projected at an angle. How should I find its velocity at a later time without mixing up speed and direction?
Think of the launch velocity as two teammates.
For a swimmer crossing a flowing river, when do I aim upstream and when do I aim straight across?
First decide the target.
What does “Resolving a vector into components” actually mean in Motion in a Plane, and why does it matter for JEE?
A vector is one arrow, but we may replace it by perpendicular x- and y-parts that together produce exactly the same effect. If the vector A makes angle theta with +x, then A_x = A cos(theta) and A_y = A sin(theta); signs come from the actual directions, not from the formula.
I keep getting “Resolving a vector into components” questions wrong in Motion in a Plane. What's the trap?
writing both components positive even when the arrow points left or downward.
What does “Independent horizontal and vertical motion” actually mean in Motion in a Plane, and why does it matter for JEE?
Gravity changes only the vertical velocity of a projectile. Horizontally, velocity stays constant when air resistance is ignored. The two motions share the same clock but otherwise evolve independently.
I keep getting “Independent horizontal and vertical motion” questions wrong in Motion in a Plane. What's the trap?
using the resultant speed as the horizontal speed throughout the flight.
What does “Projectile trajectory” actually mean in Motion in a Plane, and why does it matter for JEE?
Eliminating time from x = u cos(theta)t and y = u sin(theta)t - gt^2/2 gives a quadratic y(x), so the ideal projectile path is a parabola.
I keep getting “Projectile trajectory” questions wrong in Motion in a Plane. What's the trap?
assuming the speed is constant because the path looks smooth.
What does “Relative velocity in two dimensions” actually mean in Motion in a Plane, and why does it matter for JEE?
The velocity of A as seen from B is v_A/B = v_A - v_B. This subtraction explains rain direction, river crossings and moving-platform questions.