Answer:
Water breaking down into hydrogen and oxygen is a decomposition reaction
Hydrogen and oxygen combining to form water is a synthesis reaction
Explanation:
A decomposition reaction is a chemical reaction that involves the breakdown of a chemical reactant entity into two or more simpler product fragments
Water H₂O undergoes a decomposition reaction by breaking down into hydrogen, H₂,, and oxygen, O₂, as follows;
2H₂O (l) → 2H₂ (g) + O₂ (g)
A synthesis reaction is a reaction that involves the chemical combination of two or more dissimilar molecules or atoms to produce a different compound or molecule
Water, H₂O, is formed by a synthesis reaction of hydrogen, H₂,, and oxygen, O₂, combining as follows;
2H₂ + O₂ → 2H₂O
To solve this problem it is necessary to apply the concepts related to Dopler's Law. Dopler describes the change in frequency of a wave in relation to that of an observer who is in motion relative to the Source of the Wave.
It can be described as

c = Propagation speed of waves in the medium
= Speed of the receiver relative to the medium
= Speed of the source relative to the medium
Frequency emited by the source
The sign depends on whether the receiver or the source approach or move away from each other.
Our values are given by,
Velocity of car
velocity of motor
Velocity of sound
Frequency emited by the source
Replacing we have that



Therefore the frequency that hear the motorcyclist is 601.7Hz
The frictional force is 39.4 N
Explanation:
We can solve this problem by applying Newton's 2nd law of motion: in fact, the net force acting on the block is equal to the product between its mass and its acceleration. So we can write

where
is the net force
m is the mass
a is the acceleration
Here we know that the box is moving with constant velocity, so its acceleration is zero:

This means that the net force is also zero:

The net force on the block is given by the applied force, forward, and the frictional force, backward:

where
is the applied force
is the frictional force
Therefore, solving for
,

Learn more about friction:
brainly.com/question/6217246
brainly.com/question/5884009
brainly.com/question/3017271
brainly.com/question/2235246
#LearnwithBrainly