Question

A hunter is riding an elephant of height 4m moving in straight line with uniform speed of 2m/sec. he sights a deer running with a speed v in front at a distance 45m moving perpendicular to the direction of motion of the elephant. if hunter can throw his spear with a speed of 10m/sec. relative to the elephant, then at what angle  to it's direction of motion must he throw his spear horizontally for a successful hit. find also the speed ‘v' of the deer.

Answer 1

its the question was wrong bcz bother in iit I am doing this question the ans was not mathced with iit ans key...

Answer 2

Answer:

Angle= 37 degrees and Velocity of the deer=6 m/s

Explanation:

Let us consider that the spear and the deer are in X-Y Plane

So, the height of the elephant is in z-axis

by second eqn. of motion,

⇒4= 1/2 g$t^{2}$

∴ t=2/ $\sqrt{5}$

Ux= (10cosθ + 2)m/s                                   (Initial velocity of the spear )

Using 2nd eqn. of motion along x-axis, we get

Sx = Uxt+ 1/2Ax$t^{2}$

⇒ 4$\sqrt{5}$ = (10cosθ + 2) × 2/

⇒ cosθ = 4/5

⇒  θ = 37°

Now,

Velocity of the deer = Y- component of the velocity of spear

                                 = 10 sin37°

                                 = 10×3/5

                                 = 6 m/s