A positive acceleration indicates that the object sped up. This means that if you compare the first speed to the second, the second speed should be higher.
A negative acceleration indicates that the object has slowed down. This means that if you compare the first speed to the second, the second speed should be lower.
If an acceleration is 0, it means that it neither slowed down nor sped up.
Now let us analyze your problem by listing down the speed and the time:
At noon: 4 mi/hr
12:30 : 6 mi/hr
2:30 : 2 mi/hr
From noon to 12:30, you will notice that there is an increase in speed. This means that Tommy had a positive acceleration. (Rules out D.)
From 12:30 to 2:30, there is a decrease in speed. This would indicate that Tommy had a negative acceleration. (Rules out C.)
No speed was the same, so acceleration was never 0. (Rules out A.)
From the assumptions above, we can now deduce that the answer is B.
Answer:
the spotlight effect.
Explanation:
The spotlight effect is a tendency to think that people get noticed more often than they really do. It is an overestimation of the situation regarding the concern of getting observed. It concerns the self-confidence of an individual. For example, an individual feels that everybody in a party would notice him for a bad pair of shoes while in reality, it does not concern them.
As per the question, the overestimation of people's reaction is known as the spotlight effect.
Answer:
The mixture is made up of different atoms and pure substance is made up of same type of atom.
The main difference is that mixture can be separated into its component by physical mean while pure substances can not be separated by physical process
Explanation:
Mixture:
- The properties of the mixture are not same and contains the properties of all those component present in it.
- it is a combination of one or more Pure substances and can be separated by simple physical methods.
- it have varying boiling and melting point
Examples are:
- mixture of salt and sand
- Salt water is mixture of water and NaCl and can be separated by physical mean.
- Alloys: its a mixture of different metal
- Air: mixture of gases
Pure Substance:
Pure substances are those made of same type of atoms all elements and compounds are pure substances.
- it can not be separated by simple physical mean
- it have very constant and consistent melting and boiling point
Examples are:
- Water : contain only water molecule
- All elements: all elements are pure substance made of same atoms
- All compounds: can not be separated by physical mean.
Number of molecules NH₃ = 4.45 x 10²²
<h3>Further explanation
</h3>
A mole is a number of particles(atoms, molecules, ions) in a substance
This refers to the atomic total of the 12 gr C-12 which is equal to 6.02.10²³, so 1 mole = 6.02.10²³ particles
Can be formulated :
N = n x No
N = number of particles
n = mol
No = 6.02.10²³ = Avogadro's number
mol of NH₃ = n = 0.074
So the number of molecules :
