Please answer this question for me and explain why.

Physics

1 answer:

horsena [70]3 years ago

7 0

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.

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7 0

3 years ago

Surface tension ____. a. is the inward force which tends to minimize the surface area of a liquid b. may be increased by deterge

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Answer:

Surface tension ____. a. is the inward force which tends to minimize the surface area of a liquid b. may be increased by detergents c. is decreased by hydrogen bonding d.

Note: option d is missing

The correct answer to the question is "option A (is the inward force which tends to minimize the surface area of a liquid)"

Explanation:

Surface tension is the most important for small fluid bodies. The surface comes under tension from the imbalanced forces and is often expressed as an amount of force exerted in the surface perpendicular to a line of unit length and it is a direct measure of energy loss per unit area of a surface.

The resistance that a surface shows against extension is a proof that an internal surface tension is present in the surface. Formula for measuring surface tension is: gamma equals force divided by length. The SI unit is newton per meter, dyne per centimeter is also used.

Water has a high surface tension because the water molecules on the surface are pulled together by strong hydrogen bonds. Surface tension of a liquid surface is that property of that liquid surface that makes it act like a stretched elastic sheet. Example of effect of surface tension on water is the flotation of objects denser than water, the separation of oil and water due to tension which arises in surface between dissimilar liquids. In the surface tension of liquid, the net force of attraction acting on the molecule is zero.