The answer is B.
A cannot be the answer is melting is a physical change. No chemical reaction took place.
B is the answer as it is a EXOTHERMIC REACTION so heat will be given off.
C cannot be the answer as dissolving is basically atoms becoming ions, not a chemical reaction whereby a reactant reacts with another reactant to form a product.
D cannot be the answer. Same reason as for why A is not the answer.
Cheers.
The frequency of the wave is 6800 Hz
<u>Explanation:</u>
Given:
Wave number, n = 20
Speed of light, v = 340 m/s
Frequency, f = ?
we know:
wave number = 

Therefore, the frequency of the wave is 6800 Hz
Answer:
The pressure after passing the valve is 23,8 [Kpa] ( 0,234 atm) and the pressure drop is about 1,53 [Kpa]
Explanation:
We need to use the formula of bernoulli, in the attached image we can see the fluid throw the pipe, we also can calculate the velocity inside the pipe using the flow rate and the cross sectional area.
For this case, we don't use the elevation difference and therefore those terms can be cancelled.
When the area has reduced the velocity of the fluid is increased but there is a drop pressure through the valve.
The net force needed to lift a full grocery sack uniformly is 32.115 N.
<h3>What is Net force?</h3>
When two or more forces are acting on the system of objects, then the to attain equilibrium, net force must be zero.
Given the weight of sack W = 210N and the acceleration a = 1.5m/s².
The mass of the sack will be
m = Weight / acceleration due to gravity
m = 210 N/9.81 m/s²
m = 21.41 kg
Using Newton's second law, the net force will be
F = mass x acceleration
F= 21.41 x 1.5
F = 32.115 N
Thus, the net force is 32.115 N.
Learn more about net force.
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