Answer:
The speed decreases.
Explanation:
This can be explained using the conservation of linear momentum.
Since there is no friction, the initial moment of the train must be equal to its linear moment after it is filled with water.
the initial linear momentum is

where
is the initial mass of the train, and
the initial speed of the train.
And linear momentum after the water filled the train car is

where
is mass of the train after the rain, and
the speed of the train after the rain
<u>the equality must be fulfilled:</u>

We know that if water is added to the train,
that is the mass after the water is added, is greater than
which is the mass of the train without the water.
Therefore, in order for the conservation of the linear momentum to be fulfilled: 
the speed after the water is added (
) must be smaller than the initial train speed (
) . So the speed of the car decreases.
Answer:
The cork moves up and down.
Explanation:
The cork moves up and down because of the waves produce due to tapping the surface of water. The cork experience movement due to placed on the water surface so when the wave passes through the medium by tapping of water, movement of cork also occur. Cork has high volume and lower mass so it floats on the water surface and experience movement due to waves.
In mathematics, a percentage is a number or ratio expressed as a fraction of 100.
Answer: A projectile which is fired horizontally is being constantly acted upon by acceleration due to gravity, acting vertically downwards. Hence, it does not follow a straight line path. Also Why a projectile fixed along the horizontal not follow a straight line path? Because the projectile fired horizontally is constantly acts upon by acceleration due to gravity acting vertically downwards.
Explanation:
Hope this helped :)