This is so easy freezing and boiling, are you in 4th?
Complete Question
A spherical wave with a wavelength of 2.0 mm is emitted from the origin. At one instant of time, the phase at r_1 = 4.0 mm is π rad. At that instant, what is the phase at r_2 = 3.5 mm ? Express your answer to two significant figures and include the appropriate units.
Answer:
The phase at the second point is 
Explanation:
From the question we are told that
The wavelength of the spherical wave is 
The first radius is 
The phase at that instant is 
The second radius is 
Generally the phase difference is mathematically represented as

this can also be expressed as

So we have that

substituting values



Answer:
1331.84 m/s
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity = 0
s = Displacement = 490 km
a = Acceleration
g = Acceleration due to gravity = 1.81 m/s² = a
From equation of linear motion

The speed of the material must be 1331.84 m/s in order to reach the height of 490 km