Sound waves come from mechanical vibrations in solids, liquids, and gases. ... When a sound or light wave strikes an object, it is already vibrating at some particular frequency. If that frequency happens to match the resonant frequency of the object it's hitting, then you'll get what's called resonance.
Answer:
Friction = 5 N
Explanation:
As we know that block is moving at constant speed
So the acceleration of the block is zero
So we will have

for net force to be zero
Force exerted on the object by external system must be counter balanced by the force of friction
So we have

so we have

Either convection or thermal energy
Explanation:
The electrostatic forces are conservative forces!
The mainly property of the conservative fields is 
In spherical coordinates the field's expression is:

and the curl expression is:

to find the expression for the potential function associated:
