Answer:The frequency of the echo is slightly decreased
Explanation:
Given
speed of boat 
cliff is
away
when boat is still , suppose t is the time taken by the echo to reach observer on the boat
But as soon as boat starts moving the distance between cliff and boat decreasing and time for echo to reach observer also decreases
and we know 
therefore frequency of the echo slightly decreased.
Answer:PHARMING
Explanation:
Social engineering can be defined as an attempt to manage,change and regulate the future development and the behaviour of a society.
Common types of social engineering attack include; Watering hole, Pretexting, Phishing,Whaling attack, Baiting, PHARMING, and so on.
PHARMING is an attempt to redirect internet traffic from a legitimate site to a different identical-looking site. PHARMING is a spamming practice, a cyberattack and also, a type of phishing in which hackers use in stealing personal information from people on the internet.
PHARMING is done through the injection of malicious data or code into the victims' computer system. This injection is known as the DNS cache poisoning.
Answer:
300 Joules
Explanation:
Just use the Work formula:
W = F . D
W = 10 . 30
W = 300 Joules