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

Answer:
The frequency does not depend on the amplitude for any (ideal) mechanical or electromagnetic waves.
In electromagnetism we have that the relation is:
Velocity = wavelenght*frequency.
So the amplitude of the wave does not have any effect here.
For a mechanical system like an harmonic oscillator (that can be used to describe almost any oscillating system), we have that the frequency is:
f = (1/2*pi)*√(k/m)
Where m is the mass and k is the constant of the spring, again, you can see that the frequency only depends on the physical properties of the system, and no in how much you displace it from the equilibrium position.
This happens because as more you displace the mass from the equilibrium position, more will be the force acting on the mass, so while the "path" that the mass has to travel is bigger, the mas moves faster, so the frequency remains unaffected.
Answer:
c = 3.00E108 m/s = 3.00E5 km/s
t = S / v = 3.84E5 / 3.00E5 = 1.28 sec
Body Fossils and Trace Fossils.
Hope I helped and good luck with school. Bye!