Question

Take $z=$axis as vertical and $x-y$ plane as horizontal. A particle '$A$' is projected with velocity $4\sqrt{2}m{s}^{-1}$ making an angle ${45}^{\circ }$ to the horizontal. Particle $B$ is projected at $5m{s}^{-1}$ at an angle $\theta ={\tan }^{-1}\left(\frac{1}{3}\right)$ to $y$ axis in $y-z$ plane then velocity of $B$ wrt $A$

• A. has its initial magnitude $5m{s}^{-1}$
• B. magnitude will change with time
• C. lies in the $xy$ plane
• D. will initially make an angle $(\theta +\frac{\pi }{2})$ with $+x$ axis

Answer 1

Answer: (A)

has its initial magnitude $5m{s}^{-1}$

As we don't know velocity of particle 'A' ( It's x & y components are not known), question can't be answered.

However option 'B' is wrong as relative acceleration of particles is zero, so relative velocity between two will remain same till one of the two particles hit the ground.

Option 'C" is also wrong as z components of velocities of 'A' & 'B' are not same. Hence there will be some relative velocity in z direction.