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:
7 m/s
Explanation:
Acceleration, 
Where v and u are the final and initial velocities of the Justine respectively, t is the time taken for Justin to attain final velocity.
Making v the subject then
v=at+u
Taking u as zero then
Substituting 3.5 for t, 2 as a then
v=3.5*2=7 m/s
The answer is the same as many workers needed
Answer:
B) 35 W
Explanation:
Force applied by child = 75 N = F
Distance travelled by child = 42 m = d
Time traveled for is 1.5 min = 1.5×60 = 90 seconds = t
Work done by the child
W = Fdcosθ
⇒W = 75×42cos0
⇒W = 3150 Joule
Power is defined as work done per unit time

∴ The average power generated by the child is 35 W
use F = ma
F : force m : mass a : acceleration
so
f = 5kg * 20 m/s2 = 100 N