Answer:
The answer is "between 20 s and 30 s".
Explanation:
Calculating the value of positive displacement:
Calculating the value of negative displacement upon the time t:
That's why its value lie in "between 20 s and 30 s".
Answer:
It will take 4 sec rock to comes its original point
Explanation:
It is given that the rock comes to its original point
So displacement S = 0 m
Initial velocity u = 19.6 m/sec
Acceleration due to gravity 
According to second equation of motion 
t = 4 sec
Answer:
ºC
Explanation:
First, let's write the energy balance over the duct:
It says that the energy that goes out from the duct (which is in enthalpy of the mass flow) must be equals to the energy that enters in the same way plus the heat that is added to the air. Decompose the enthalpies to the mass flow and specific enthalpies:
The enthalpy change can be calculated as Cp multiplied by the difference of temperature because it is supposed that the pressure drop is not significant.
So, let's isolate 
:
The Cp of the air at 27ºC is 1007
(Taken from Keenan, Chao, Keyes, “Gas Tables”, Wiley, 1985.); and the only two unknown are and Q.
Q can be found knowing that the heat flux is 600W/m2, which is a rate of heat to transfer area; so if we know the transfer area, we could know the heat added.
The heat transfer area is the inner surface area of the duct, which can be found as the perimeter of the cross section multiplied by the length of the duct:
Perimeter:
Surface area:
Then, the heat Q is:
Finally, find the exit temperature:
=27.0000077 ºC
The temperature change so little because:
- The mass flow is so big compared to the heat flux.
- The transfer area is so little, a bigger length would be required.
Answer:
Explanation:
3. Newton’s third law explains how every action has an equal but opposite reaction, meaning that forces comes in pairs. While the locomotive’s wheels are pushing back against the ground as the action force, the ground is producing a reaction force towards the locomotive, propelling it forward. Another pair of forces that act on the locomotive is gravity and normal force. While gravity is pulling the locomotive towards the ground, the normal force the ground exerts on the locomotive is why the locomotive doesn’t fall through the ground.
4. The force of Earth’s gravity on the Sun is weaker than the force of the Sun’s gravity on Earth. The Sun’s attraction affects the motion of Earth more than the Earth’s attraction affects the Sun’s motion because according to Newton’s second law, force has mass as one of its factors. The Sun has a significantly higher mass than Earth, meaning that its force of gravity would also be significantly higher. Newton’s third law is why the Earth doesn’t get marginally closer to the Sun, stating that every action has an equal and opposite reaction. As the Sun is pulling Earth towards itself, Earth is pulling away from the Sun.
<span>Two objects move toward each other because of gravitational attraction. As the objects get closer and closer, the force between them increases. </span>
