Question

A projectile is launched at angle $\theta$ to the horizontal from point $L$ and it hits the target $T$ on level ground. During the entire motion:

Column I		Column II
i	Magnitude of radial acceleration	p	remains constant
ii	Magnitude of tan gential acceleration	q	either always de creases or always increases
iii	Power delivered by gravity	r	First increases, then decreases
iv	Total acceleration	s	First decreases, then increases

Now match the given columns and select the correct option from the codes given below. Codes:

• A. i—p, ii—q, iii—r, iv—s
• B. i—r, ii—s, iii—r, iv—p
• C. i—s, ii—p, iii—q, iv—r
• D. i—p, ii—r, iii—p, iv—s

Answer 1

Answer: (B)

$a_r=g\cos \alpha ,a_t=g\sin \alpha$
first decreases and then increases.
So radial acceleration increases and then decreases, Tangential acceleration decreases and then increases

Power due to gravity $=\vec{m}g\cdot \vec{v}$
$=mgv\cos \left(\frac{\pi }{2}+\alpha \right)=-mgv\sin \alpha$
$v$ sin first decreases and then increases.
So power (power is negative here) increases and then increases
Total acceleration is g which always remains constant