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3 years ago

A rock of mass m is twirled on a string in a horizontal plane. The work done by the tension in the string on the rock is..

Physics

1 answer:

anyanavicka [17]3 years ago

6 0

Answer:

work done by tension force on the twirled stone must be ZERO always

Explanation:

As we know that work done by a force on an object is given as

$W = F.d$

$W = Fdcos\theta$

here we know that

$\theta$ = angle between force and displacement

now we know that tension in the string and displacement of the object is always perpendicular to each other when the rock is twirled in circular path.

so we can say for this motion of the stone

$cos\theta = 0$

so work done by tension force on the twirled stone must be ZERO always

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(5) A 4 kg. object rests on a flat, horizontal surface with a static

baherus [9]

Answer:

F = 9.81 [N]

Explanation:

To solve this problem we must use Newton's third le which tells us that the sum of forces on a body that remains static must be equal to one resulting from these forces in the opposite direction.

Let's perform a summation of forces on the vertical axis-y to determine the normal force N.

∑F = 0 (axis-y)

$N - m*g = 0$

where:

m = mass = 4 [kg]

g = gravity acceleration = 9.81 [m/s²]

$N - (4*9.81)=0\\N = 39.24 [N]$

Now we know that the frictional force can be calculated using the following equation.

f = μ*N

where:

f = friction force [N]

μ = friction coefficient = 0.25

N = normal force = 39.24 [N]

Now replacing:

$f = 0.25*39.24\\f = 9.81[N]$

Then we perform a sum of forces on the X-axis equal to zero. This sum of forces allows us to determine the minimum force to be able to move the object in a horizontal direction.

∑F = 0 (axis-x)

$F-f=0\\F-9.81=0\\F= 9.81[N]$

If the coefficient was smaller, a smaller force (F) would be needed to start the movement, this can be easily seen by replacing the value of 0.25, by smaller values, such as 0.1 or 0.05.

If the coefficient were larger, a larger force would be needed.

3 0

3 years ago

What is the concentration of H+ ions at a pH = 8?

skelet666 [1.2K]

Taking into account the definition of pH and pOH, the concentration of H⁺ ions at pH=8 is 1×10⁻⁸ M and the concentration of OH⁻ ions at pH=8 is 1×10⁻⁶ M.

<h3>Definition of pH</h3>

pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:

pH= - log [H⁺]= - log [H₃O⁺]

<h3>Definition of pOH</h3>

Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

<h3 /><h3>Relationship between pH and pOH</h3>

The following relationship can be established between pH and pOH:

pOH + pH= 14

<h3>Concentration of H⁺ ions</h3>

In this case, pH=8. Replacing in the definition of pH:

8= - log [H⁺]

Solving:

Finally, the concentration of H⁺ ions at pH=8 is 1×10⁻⁸ M.

<h3>Concentration of OH⁻ ions</h3>

Being pH= 8, pOH is calculated as:

pOH + 8= 14

pOH= 14 - 8

pOH= 6

Replacing in the definition of pOH the concentration of OH⁻ ions is obtained:

- log [OH⁻]= 6

Solving

Finally, the concentration of OH⁻ ions at pH=8 is 1×10⁻⁶ M.

Learn more about pH and pOH:

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7 0

2 years ago

Describe the energy transformations that occur when you bounce a ball?

Gemiola [76]

The transformation is kinetic energy

7 0

4 years ago

Read 2 more answers

Which sequence shpes the steps of the proces of science in an order in which they might occur?

ivanzaharov [21]

The steps of the process of science in an order in which they might occur

exploration >> hypothesis >> prediction >> experiment.

The correct option is D.

<h3>Explanation:</h3>

A series of sequential steps are included in the scientific method, which is how knowledge in the scientific field is acquired.
When a question arises from observing the natural world, a hypothesis is a predetermined explanation of the question.
Experimental and/or observational procedures must be used to test a hypothesis and determine whether it is true or false.

<h3>What are some fundamental scientific procedures?</h3>

When scientists conduct research and study, they use specific science process skills. The thinking processes that scientists, teachers, and students use when conducting science include observing, categorizing, communicating, measuring, inferring, and predicting.

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I understand that the question you are looking for is:

Which sequence shows the steps of the process of science in an order in which they might occur?

A. exploration, question, opinion, conclusion, hypothesis

B. question, observation, experiment, analysis, prediction

C. experiment, conclusion, exploration, application

D. exploration, hypothesis, prediction, experiment

6 0

2 years ago

Suppose that an object is moving along a vertical line. Its vertical position is given by the equation L(t) = 2t3 + t2-5t + 1, w