Question

Two particles are projected simultaneously in the same vertical plane from the same point, with different speeds $u_1$ and $u_2$, making angles ${\theta }_1$ and ${\theta }_2$ respectively with the horizontal, such that $u_1\cos {\theta }_1=u_2\cos {\theta }_2$. The path followed by one, as seen by the other (as long as both are in flight) is:

• A. A horizontal straight line
• B. A vertical straight line
• C. a parabola
• D. A straight lline making an angle $|{\theta }_1-{\theta }_2|$ with the horizontal

Answer 1

The correct option is B A vertical straight line

As both particles have same acceleration, their relative acceleration is zero. Hence the path of motion of one with respect to other will be a straight line and the line is vertical because their relative velocity along horizontal is zero.