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DIA [1.3K]
3 years ago
11

A train is moving in the positive direction down a track. First the train speeds up, and then it slows down. What is its acceler

ation?
A. The train has positive acceleration throughout.
B.The train has negative acceleration throughout.
C.The train first has positive acceleration and then negative acceleration.
D.The train first has negative acceleration and then positive acceleration.
Physics
2 answers:
tatuchka [14]3 years ago
8 0
C.

The train first sped up, giving it a positive acceleration in the beginning. This eliminates D since that choice states that it begins with a negative acceleration. This also eliminates B since that choice states that the train only had a negation acceleration.

Next, the train slows down, giving it a negative acceleration. We’re looking for the answer choice that starts with a positive acceleration and ends with a negative one. This makes C the correct answer. Hope this helps!
Marina86 [1]3 years ago
8 0

Answer:

The answer is <u><em>The train first has positive acceleration and then negative acceleration. </em></u>

<u><em></em></u>

Explanation: I answered the question right on my online school quiz.

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A barge of mass 5.00 ×104 kg is pulled along the Erie Canal by two mules, walking along towpaths parallel to the canal on either
boyakko [2]

Answer:  219,344.5 j

Explanation:

from the question we have the following parameters

mass of barge (m) = 5 x 10^4 kg

angle of ropes (θ) = 45 degrees

force by each mule (F1) = 1.10 kN = 1100 N

force by each mule (F2) = 1.10 kN = 1100 N

distance (s) = 141 m

work done by the mules = force x cos θ x distance

since we are calculating the force of both mules we have to both mules before we can use in the equation

force = 1100 + 1100 = 2200 N

work done =  2200 x cos (45) x 141

work done = 219,344.5 j

5 0
3 years ago
Which actions are evidence that a chemical reaction has occurred? Check all that apply. a change in color the formation of a pre
NeTakaya

Answer:

  1. a change in color
  2. the formation of a precipitate
  3. the formation of bubbles

Explanation:

In a chemical reaction, there is always a rearrangement of atoms within the molecules of reactants to form new products. Such a change is different from changes in the physical form of molecules, e.g. shape.

Thus, according to this criteria, only three options are correct in the given question. A change in color is definitely an indication of chemical reaction because the emission of light before and after cannot be changed unless molecules are rearranged to form a new chemical. Likewise, precipitates form when a reaction takes place between chemically dissolved molecules to form less or not dissolvable compounds. In the end, the configuration of bubbles also indicates that the reaction has taken place because new gases are being released.

On the other hand, change in shape is a physical change because the composition doesn't need to also been changed. An example is the ice formation from water. Same is the case with "change of clear liquid to cloudy" because the addition of non-reactive substances could change the nature of liquid to cloudy however the reaction doesn't need to have taken place.

8 0
3 years ago
Read 2 more answers
A diode, which allows current to flow in one direction only, consists of two types of semiconductors joined together.
Nata [24]

Answer:

True.

Explanation:

A diode, which allows current to flow in one direction only, consists of two types of semiconductors joined together.

A semiconductor can be defined as a crystalline solid substance that has its conductivity lying between that of a metal and an insulator, due to the effects of temperature or an addition of an impurity. Semiconductors are classified into two main categories;

1. Extrinsic semiconductor.

2. Intrinsic semiconductor.

An intrinsic semiconductor is a crystalline solid substance that is in its purest form and having no impurities added to it. Examples of intrinsic semiconductor are Germanium and Silicon.

In an intrinsic semiconductor, the number of free electrons is equal to the number of holes. Also, in an intrinsic semiconductor the number of holes and free electrons is directly proportional to the temperature; as the temperature increases, the number of holes and free electrons increases and vice-versa.

In an intrinsic semiconductor, each free electrons (valence electrons) produces a covalent bond.

6 0
4 years ago
A 33.0 g iron rod, initially at 22.7 ∘c, is submerged into an unknown mass of water at 63.3 ∘c, in an insulated container. the f
professor190 [17]
When the iron and the water reach thermal equilibrium, they have same temperature, T=58.5^{\circ}C.
We can consider this as an isolated system, so the heat released by the water is equal to the heat absorbed by the iron.

The hear released by the water is:
Q_w =m_w C_{sw} \Delta T_w
where m_w is the water mass, C_{sw}=4.186 J/(g^{\circ}C) is the specific heat of the water, and \Delta T_w = 63.6^{\circ}-58.5^{\circ}=5.1^{\circ}C is the variation of temperature of the water.

Similarly, the heat absorbed by the iron is:
Q_i = m_i C_{si} \Delta T_i
where m_i = 33.0 g is the iron mass, C_{si}=0.444 J/(g^{\circ}C) is the iron specific heat, and \Delta T_i = 58.5^{\circ}-22.7^{\circ}=35.8^{\circ}C is the variation of temperature of the iron.

Writing Q_w=Q_i and replacing the numbers, we can solve to find mw, the mass of the water:
m_w= \frac{m_i C_{si} \Delta T_i}{C_{sw} \Delta T_w} =24.6 g
4 0
3 years ago
Why is si unit called coherent system
Sladkaya [172]

Answer:

The SI system is also called coherent system of units because of the following reasons: ... 1 Newton (SI unit of Force) = 1 Kg (SI unit of mass) x 1 m (SI unit of distance) / s2 (SI unit of time) , therefore 1 Newton is a coherent unit of Force.

HOPE ITS HELP

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