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Bad White [126]
3 years ago
15

6 .sınıf fen bilimleri

Physics
1 answer:
damaskus [11]3 years ago
5 0
Please translate to english.
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8. A car travels at a constant velocity of 70 mph for one hour. By the end of the second hour, the car’s velocity was 60 mph. At
Mrac [35]

<u>Answer:</u>

  Positive acceleration is in third hour and negative acceleration is in second hour.

<u>Explanation:</u>

  Velocity of car in first hour =  70 mph

  Velocity of car in second hour = 60 mph

  Velocity of car in third hour = 80 mph

   Acceleration = Change in velocity / Time

   Acceleration in second hour = (60 - 70)/1 = -10 mph²

   Acceleration in third hour = (80 - 60)/1 = 20 mph²

   So positive acceleration is in third hour and negative acceleration is in second hour.

8 0
3 years ago
A regular atom has a net charge of _____
Doss [256]
An atom is defined as having the same number of electrons (negative charge), protons (positive charge) and neutrons (no charge). This means that it will have the same amount of negative and positive charge, giving it a net zero charge. On the other hand, an ion has different amount of electrons and protons.
5 0
3 years ago
A 750-newton person stands in an elevator that is
blondinia [14]
When an elevator is accelerating downward, the normal force is equal to mg-ma (hence you feel a little lighter when accelerating downwards)

Therefore, the upward force of the elevator floor on the person must be less than 750N
8 0
3 years ago
....................................................
iragen [17]
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8 0
2 years ago
Read 2 more answers
Please answer this question for me and explain why.
horsena [70]

Answer:

D.None of these

Explanation:

The derivation of acceleration formula:

Let us call the 5kg mass m_2 and the 4kg mass m_1. If the tension in the string is T then for the mass m_2

(1). T-m_2g=-m_2a <em>(the negative sign on the right side indicates that acceleration is downwards)</em>

And for the mass m_1

(2). T-m_1g =m_1a<em> (the acceleration is upwards, hence the positive sign)</em>

Solving for T in the 2nd equation we get:

T =m_1a+m_1g,

and putting this into the 1st equation we get:

m_1a+m_1g-m_2g=-m_2a\\\\m_1a+m_2a = m_2g-m_1g\\\\a(m_1+m_2)= (m_2-m_1)g

\boxed{a= \dfrac{(m_2-m_1)}{(m_1+m_2)} g}

Back to the question:

Using the formula for the acceleration we find

a= \dfrac{(5kg-4kg)}{(5kg+4kg)} g

a = \dfrac{g}{9},

which is the acceleration that none of the given choices offer. Also, the acceleration of the two blocks is the same, because if it weren't, the difference in the instantaneous velocities of the objects would cause the string to break. Therefore, these two reasons make us decide that none of the choices are correct.

7 0
3 years ago
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