The value of specific heat for copper is 390 j/kg⋅c∘, for aluminun is 900 j/kg⋅c∘, and for water is 4186 j/kg⋅c∘. part a what will be the equilibrium temperature when a 225 g block of copper at 235 ∘c is placed in a 155 g aluminum calorimeter cup containing 835 g of water at 16.0 ∘c?

21.2 Câ    
There are a few assumptions to note before solving this problem. First assumption is that the aluminum cup is at the same temperature as the water at the start. The second assumption is that the from the copper block is transferred slowly enough that no water is lost due to boiling or evaporation, or that such loss is insignificant.    
Since the temperatures are in a range where there will be no phase changes, we can make the problem easier by arbitrary considering our starting temperature to be 16.0 âC for everything. So we'll consider the starting energy for the aluminum and water to be 0. So let's calculate the amount of excess energy the copper block has over the base temperature of 16.  
235 - 16 = 216  
216 * 390 J/kgâ‹…Câ * 0.225 kg = 19217.25 J    
We now have 19217.25 Joules of energy with which to raise the temperature of 225 grams of copper, 155 grams of aluminum, and 835 grams of water. Let's see how much energy is needed to raise the temperature of all 3 items by 1 degree.  
0.225 Kg * 390 J/kgâ‹…Câ + 0.155 kg * 900 J/kgâ‹…Câ + 835 * 4186 J/kgâ‹…Câ  
= 87.75 J/Câ + 139.5 J/Câ + 3495.31 J/Câ  
= 3722.56 J/Câ    
Now we have a simple matter of multiplication to get the temperature rise from our starting point.  
19217.25 J / 3722.56 J/Câ = 5.162374817 Câ    
So the temperature rises by 5.162374817 Câ from our starting point. Just add that to the starting point:  
16.0 Câ + 5.162374817 Câ = 21.16237482 Câ    
Finally, round to 3 significant figures, giving 21.2 Câ

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.

Not sure but i think it's b.