Question

A light body is projected with a velocity
00i+20j+20 k) ms. Wind blows along
X-axis with an acceleration of 2.5 ms. If
Y-axis is vertical then the speed of particle
after 2 second will be (g 10 m )
(A) 25 ms (B) 10/5 ms
(0) 30 m
(D) None of these​

Answer 1

Answer:

Option (D) None of these

Explanation:

Given

Velocity of the body = $20\hat j+20\hat k$

Acceleration of the wind in the x direction = 2.5 m/s^2

Since the wind will be blowing opposite to the motion

Therefore, it will be negative

or, $\vec a=-2.5\hat i$

After 2 seconds the component of the velocity in the x direction will be

v = u + at   (Using first equation of motion)

v = 0 - 2.5 × 2

or v = -5 m/s

Also the acceleration due to gravity will be acting in the y-direction

Therefore, velocity in y-direction after 2 seconds

v'= u'-gt

v'= 20 - 10 × 2

or, v' = 0

Therefore the velocity vector after 2 seconds will be

$-5\hat i+20\hat k$

Speed of the particle

$=\sqrt{(-5)^2+20^2}$

$=20.61$ m/s