
Actually Welcome to the Concept of the Wave Optics.
Whenever the waves are out of phase they form a DESTRUCTIVE interference.
thus,
Destructive Interference occurs when two waves are out of phase.
Answer: 10 s, 30 m/s , 150 m
Explanation:
Given
The speed of motorcyclist is 
The initial speed of a police motorcycle is 
acceleration of police motorcycle is 
Police will catch the motorcyclist when they traveled equal distances
distance traveled by motorcyclist in time t is

Distance traveled by Police in time t is

put 

Police officer's speed at that time is

Distance traveled by each vehicle is

Answer:
t = 2 hours
Explanation:
Given that,
Distance of the town, d = 90 miles
Speed, v = 45 mph
We need to find the time to get there. The speed of an object is given by :

Where
t is time

So, the required time is 2 hours.
Answer:
upward force acting = 261.6 N
Explanation:
given,
mass of gibbon = 9.4 kg
arm length = 0.6 m
speed of the swing
net force must provide

force of gravity = - mg

= 
= 
=9 x 29.067
= 261.6 N
upward force acting = 261.6 N
Answer:
attracting iron and producing a magnetic field