If you throw a rock into a pond, it creates a wave in the water. what is responsible for creating an electromagnetic wave? hints

surface wave of water is due to the disturbance of medium particles

this is also known as mechanical waves

In mechanical waves we need a mechanical medium to disturb the medium particles which will produce the disturbance

While electromagnetic waves do not require any medium and it can propagate through vacuum

Electromagnetic waves are propagation of electric and magnetic field which is due to oscillation of charge.

So electromagnetic field requires to and from motion of charge particle in which time dependent electric field will induce magnetic field and then they induce each other and propagate in the medium

the velocity you are looking for is made up of two parts: horizontally velocity, vh, and its vertical velocity, vv. the actual velocity of the ball will be these two parts added together, and because velocity is a vector then they will need to be added vectorially.  

neglecting air resistance etc etc.,  

the horizontal velocity component will be constant (because there is no accelerating force in the horizontal direction.  

vh = 8 ms-1  

the vertical velocity component has an accelerating force: 'g'.  

using v = u +at where a = g = 9.81 ms-2.  

the vertical component of velocity, vv = 0 + gt = vv =9.81 x 2  

vv = 19.62 ms-1 . the zero appears because the virtical component of velocity at time t=0 is zero. remember, the ball was thrown horizontally.  

how fast it will be moving (it actual path (being a parabola )) will be the vector sum of these two.  

adding vectorally gives: -  

v = sqr root (8^2 + 19.62^2) = sqr root(64+384.9) = 21.18 or 21.2 ms-1

are there answer choices to this question? this seems like a question where you have options to choose from.