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2 years ago

Which statements describe properties of stars? Check all that apply.

2 answers:

7 0

One, three and five are correct.

Although if the second statement is saying that stars use gravitational force to support nuclear fusion which in turn produces energy then that would be correct, but I don’t think so :)

swat322 years ago

4 0

Answer:

Stars produce energy through nuclear fusion.
Stars are massive objects composed of gas.
Stars are composed primarily of hydrogen and helium.

Explanation:

Stars are massive objects that have a large gravitational field, which drives the star to contract on itself, which is why fusion occurs: in the center of the star the nuclei of atoms are already so close due to gravity and high temperatures that bind. This is what is called nuclear fusion and is the energy source of a star.

On the other hand yes, the main elements of a star are hydrogen and helium (two hydrogen nuclei fuse to make helium), this makes the star mainly a huge ball of gas so there is no solid surface where you can stand on.

And about water on a star, that is not possible. Temperatures on stars are very vey high that watter could not exist in a liquid form on them.

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Valency of oxygen is two. why??

AlexFokin [52]

Answer:

Tha valency of Oxygen is 2 because it need two atom of hydrogen to form water.

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2 years ago

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Instantaneous speed is measured

VMariaS [17]

Answer:

C. At a particular instant

Explanation:

Speed is the defined as the ratio between the distance covered by an object and the time taken:

$v=\frac{d}{t}$

where d is the distance and t the time.

However, there are two possible measurements of speed:

- Average speed: this is the speed measured over a non-zero time interval (for example: a car moving 100 metres in 5 seconds; its average speed is

$v=\frac{100 m}{5 s}=20 m/s$

- Instantaneous speed: this is the speed of an object measured at a particular instant in time, so for a time interval that tends to zero. So, in the previous example, the average speed is 20 m/s but the instantaneous speed of the car at various instants of time can be different from that value.

7 0

2 years ago

A powerful motorcycle can produce an acceleration of 3.50 m/s2 while traveling at 90.0 km/h. At that speed the forces resisting

IrinaK [193]

Answer:1265 N

Explanation:

Given

acceleration of motorcycle $\left ( a\right )=3.5 m/s^2$

Velocity $\left ( v\right )=90 km/h\approx 25m/s$

Air friction and Friction $\left ( f\right )=425 N$

mass of the motorcycle with rider $\left ( m\right )=240 Kg$

Applying Forces on motorcycle

$F_{engine}-f=ma$

$F_{engine}=f+ma$

$F_{engine}=425+240\left ( 3.5\right )$

$F_{engine}=425+840=1265 N$

5 0

3 years ago

Define wheel and axle in science terms

topjm [15]

Answer:

A simple machine consisting of an axle to which a wheel is fastened so that torque applied to the wheel winds a rope or chain onto the axle, yielding a mechanical advantage equal to the ratio of the diameter of the wheel to that of the axle.

5 0

2 years ago

The three components of velocity in a velocity field are given by u = Ax + By + Cz, v = Dx + Ey + Fz, and w = Gx + Hy + Jz. Dete

Alexxandr [17]

Answer:

The relationship is only between the coefficients A, E and J which is:

$A + E + J = 0$ . The remaining coefficients can be anything without any constraints.

Explanation:

Given:

The three components of velocity is a velocity field are given as:

$u = Ax + By + Cz\\\\v = Dx + Ey + Fz\\\\w = Gx + Hy + Jz$

The fluid is incompressible.

We know that, for an incompressible fluid flow, the sum of the partial derivatives of each component relative to its direction is always 0. Therefore,

$\frac{\partial u}{\partial x}+\frac{\partial v}{\partial y}+\frac{\partial w}{\partial z}=0$

Now, let us find the partial derivative of each component.

$\frac{\partial u}{\partial x}=\frac{\partial }{\partial x}(Ax+By+Cz)\\\\\frac{\partial u}{\partial x}=A+0+0=A\\\\\frac{\partial v}{\partial y}=\frac{\partial }{\partial y}(Dx+Ey+Fz)\\\\\frac{\partial v}{\partial y}=0+E+0=E\\\\\frac{\partial w}{\partial z}=\frac{\partial }{\partial z}(Gx+Hy+Jz)\\\\\frac{\partial w}{\partial z}=0+0+J=J$

Hence, the relationship between the coefficients is:

$A+E+J=0$

There is no such constraints on other coefficients. So, we can choose any value for the remaining coefficients B, C, D, F, G and H.

6 0

2 years ago