Echo sounding is a type of SONAR used to determine the depth of water by transmitting sound pulses into water. The time interval between emission and return of a pulse is recorded, which is used to determine the depth of water along with the speed of sound in water at the time.
Answer:

Explanation:
The vector that point from point P1 to point P2 its found simply by taking the vector at which point P2 its located and subtracting the vector at which point P1 its located:

So:



Radiation: Getting sunburnt on a beach.
- The sun’s radiation (no direct contact) is what causes the skin to burn.
Radiation: Microwave cooking food
- Microwaves use radiation to heat the food inside of it; between radio waves and infrared radiation on the electromagnetic spectrum
Conduction: Touching a hot car seat in the summer
- Conduction is the transfer of heat by direct contact (hand to seat).
Conduction: Burning yourself with a curling iron (Similar to above; direct contact).
Convection: An ocean breeze
- Convection near coastlines cause the transfer of energy; water warms and cools slower than land.
Conduction: Sliding down a hot metal slide in august
- You are in direct contact with the slide, which is hot due to the temperature.
Convection: Water in a boiling pot of macaroni
- The water, a liquid, is being heated by molecular motion.
Convection: Currents deep within the earth that cause tectonic plates to move
- Convection currents drive the movement of tectonic plates in the mantle, which is fluid/molten. The currents circulate under the asthenosphere.
Weight of the carriage 
Normal force 
Frictional force 
Acceleration 
Explanation:
We have to look into the FBD of the carriage.
Horizontal forces and Vertical forces separately.
To calculate Weight we know that both the mass of the baby and the carriage will be added.
- So Weight(W)

To calculate normal force we have to look upon the vertical component of forces, as Normal force is acting vertically.We have weight which is a downward force along with
, force of
acting vertically downward.Both are downward and Normal is upward so Normal force 
- Normal force (N)

- Frictional force (f)

To calculate acceleration we will use Newtons second law.
That is Force is product of mass and acceleration.
We can see in the diagram that
and
component of forces.
So Fnet = Fy(Horizontal) - f(friction) 
- Acceleration (a) =

So we have the weight of the carriage, normal force,frictional force and acceleration.
Answer:
Explanation:
fundamental frequency, f = 250 Hz
Let T be the tension in the string and length of the string is l ans m be the mass of the string initially.
the formula for the frequency is given by
.... (1)
Now the length is doubled ans the tension is four times but the mass remains same.
let the frequency is f'
.... (2)
Divide equation (2) by equation (1)
f' = √2 x f
f' = 1.414 x 250
f' = 353.5 Hz