Kinematics Question 591

Question: A particle crossing the origin of co-ordinates at time t = 0, moves in the xy-plane with a constant acceleration a in the y-direction. If it’s equation of motion is $ \text{y = b}{{\text{x}}^{\text{2}}} $ (b is a constant), it’s velocity component in the x-direction is

Options:

A) $ \sqrt{\frac{2\text{b}}{\text{a}}} $

B)$ \sqrt{\frac{\text{a}}{2\text{b}}} $

C) $ \sqrt{\frac{\text{a}}{\text{b}}} $

D)$ \sqrt{\frac{\text{b}}{\text{a}}} $

Show Answer

Answer:

Correct Answer: B

Solution:

[b] $ \text{y = b}{{\text{x}}^{\text{2}}} $ . Differentiating w.r.t to t an both

$ \frac{\text{dy}}{\text{dx}}=\text{b2x}\frac{\text{dx}}{\text{dt}}\Rightarrow {{v _{y}}=2\text{bx}}{{v _{x}}} $

Again differentiating w.r.t to t on both sides we get

$ \frac{dv_y}{dt}=2{b}{v_x}\frac{dx}{dt+2bx}\frac{dv_x}{dt}=2{bv_x^2}+0 $

$ \frac{\text{d}}{{v _{x}}}{\text{dt}}=0, $

because the particle had constant acceleration along y-direction

$ \text{Now, }\frac{\text{d}}{{v _{y}}}{\text{dt}}=\text{a=2bv} _{x^{2}}; $

$ {v} _{x^{2}}=\frac{a}{2{b}}$

$\Rightarrow {{v _{x}}}=\sqrt{\frac{\text{a}}{\text{2b}}} $



NCERT Chapter Video Solution

Dual Pane