Answer:
12.64968 Hz
Explanation:
v = Velocity of sound in seawater = 1522 m/s
u = Velocity of dolphin = 7.2 m/s
f' = Actual frequency = 2674 Hz
From Doppler effect we get the relation

The frequency that will be received is 2661.35032 Hz
The difference in the frequency will be

Answer:
When the temperature of the coffee is 50 °C, the time will be 20.68 mins
Explanation:
Given;
The initial temperature of the coffee T₀ = 95 °C
The temperature of the room = 21°C
Let T be the temperature at time of cooling t in mins
According to Newton's law of cooling;

When the temperature is 50 °C, the time t in min is calculated as;

Therefore, when the temperature of the coffee is 50 °C, the time will be 20.68 mins
Hi there!
First of all, you have to pay attention to the question, and they are asking for something physical, and physical means to be seen on the outside.
The answer is A because you can clearly see that water is a liquid. Being a liquid is a physical property.
It wouldn't be B because I believe it would be a chemical property to react with many substances.
Hope this helps! :D
Answer:
I belive it is c
Explanation: If an object is at rest it shall stay at rest until an equal or oppisite force is applied.