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3 years ago

One of the solid reactants was treated in a coffee grinder before adding to

Physics

1 answer:

Nikitich [7]3 years ago

7 0

Answer:

C. Surface area

Explanation:

The rate of chemical reaction depends on various factors such as:

concentration and pressure
nature of reactants
temperature
surface area
presence of catalyst, etc.

Effect of surface area of reactants: the rate of a chemical reaction can be increased by increasing the the area of contact of the reacting substances. This is especially important when one or more of the reactants are solids., because only the particles of the solid that are exposed are able to take part in the reaction at each instant of time. Therefore, the greater the surface area of the solid reactant particles the faster the reaction.

The surface area of solid reactants can be increased by grinding or pelletizing, thus allowing for a greater contact between the reacting particles,

The instance in which one of the solid reactants was treated in a coffee grinder before adding to the reaction container is one way of increasing the surface area of a reactant.

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An attacker at the base of a castle wall 3.65 m high throws a rock straight up with speed 7.4m/s from a height of 1.55m above th

Natali5045456 [20]

a) Yes, the rock will reach the top

b) The final speed is 3.7 m/s

c) The change in speed is 2.4 m/s

d) The change in speed in the two situations do not agree

e) Because the kinetic energy depends quadratically on the speed, $K\propto v^2$

Explanation:

The mechanical energy of the rock at the moment it is thrown from the ground is equal to the sum of its kinetic energy and its potential energy:

$E=KE_i + PE_i = \frac{1}{2}mu^2 + mgh_i$

where

m is the mass of the rock

u = 7.4 m/s is the inital speed

$g=9.8 m/s^2$ is the acceleration of gravity

$h_i = 1.55 m$ is the initial height of the rock

Substituting, we find the initial mechanical energy of the rock

$E=\frac{1}{2}m(7.4)^2 + m(9.8)(1.55)=42.6m$ [J]

In order to reach the top of the castle, the rock should have a mechanical energy of at least

$E' = mgh'$

where

h' = 3.65 m is the heigth of the top

Substituting,

$E'=m(9.8)(3.65)=35.6m$ [J]

Since E > E', it means that the rock has enough mechanical energy to reach the top.

The final mechanical energy of the rock at the top is

$E=mgh'+ \frac{1}{2}mv^2$ (1)

where:

v is the final speed of the rock at the top

Since the mechanical energy is conserved, this should be equal to the initial mechanical energy:

$E=42.6 m$ [J] (2)

Therefore, equating (1) and (2), we can find the final speed of the rock:

$mgh' + \frac{1}{2}mv^2 = 42.6m\\v=\sqrt{2(42.6-gh')}=\sqrt{2(42.6-(9.8)(3.65))}=3.7 m/s$

Since the motion of the rock is a free fall motion (constant acceleration equal to the acceleration of gravity), we can use the following suvat equation:

$v^2 - u^2 = 2as$

where

v is the final speed, at the bottom

u = 7.4 m/s is the initial speed of the rock, at the top

$a=9.8 m/s^2$ is the acceleration of gravity

s = 3.65 - 1.55 = 2.1 m is the vertical displacement of the rock

Solving for v, we find the final speed:

$v=\sqrt{u^2+2as}=\sqrt{7.4^2 + 2(9.8)(2.1)}=9.8 m/s$

Therefore, the change in speed is

$\Delta v = v-u = 9.8 - 7.4 =2.4 m/s$

In the first situation (rock thrown upward), we have:

u = 7.4 m/s (initial speed)

v = 3.7 m/s (final speed)

So the change in speed is

$\Delta v = v-u =3.7 - 7.4 = -3.7 m/s$

While the change in speed in the second situation (rock thrown downward) is

$\Delta v = 2.4 m/s$

Therefore, we see that their magnitudes do not agree.

In both situations, the change in kinetic energy of the rock is equal in magnitude to the change in gravitational potential energy, since the total mechanical energy is conserved.

The change in gravitational potential energy in the two situations is the same (because the change in height is the same), therefore the change in kinetic energy in the two situations is also the same.

However, the kinetic energy of the rock is not directly proportional to the speed, but to the square of the speed:

$K\propto v^2$

Since the initial speed is the same for both situation (7.4 m/s), but the change in kinetic energy has opposite sign in the two situations (negative when the rock is thrown upward, positive when thrown downward), the situation is not symmetrical, therefore in order to have the same magnitude of change in the kinetic energy, the change in speed must be larger when the kinetic energy involved is lower, so in the first situation.

Learn more about kinetic energy and about potential energy:

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How do mass and velocity of an object affects mommentum?

Gelneren [198K]

I have no idea look it up maaaannnnn

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3 years ago

Which is the temperature that Fahrenheit and Celsius thermometers would

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Why are chemicals and hot objects never placed directly on the balance pan?

natita [175]

The answer is to retain the balance pan clean and to keep chemicals from mixing with other chemicals. Also some chemicals can respond with the metal of the balance pan and cause it to oxidize or corrode. Each time you use the balance pan, use weighing paper or a small dish or beaker to weigh out chemicals.

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3 years ago

What is the purpose of family?

Marrrta [24]

Answer:

Purpose of family:

Basically main role of a family towards the society is its continuity by both reproduction and interaction with each other. The main contribution of family to the society is society's continuation.

Types of families:

The family further divided into six types nowadays. Namely,

Nuclear Family
Single Parent
Extended Family
Childless Family
Step family
Grandparent Family

Defining each Family and their pros and cons :

1). Nuclear Family: The most basic kind of family is nuclear family based on two parents and their biological or adopted children. Number of children is variable, some have one and others have more than one. The main aim of the nuclear family is to up bring their kids and teach them how to socialize in the society.

Pros of nuclear family:

Both parents work and more likely financially stable
Children gets more balanced parenting
Concerned about education
Focus more on health issues both mental and physical
More socialize in the society

Cons of nuclear family:

Higher level of stress factor due to increased number of dependents
Have higher rates of disputes
Children become egotistical due to over possessive parents

2). Single Parent: Consists of either a mother or a father living with one or more than one child. Parents may initially married, separated or departed, or passed away (one of them). Like other family structures single parents also have some pros and cons.

Pros of single parent:

Close relationship with each other due to less family members
More responsible as duties are not being further divided.
Both children and parents are strong and independent

Cons of single parent:

Less income due to sole parent
May relay on financial help
Quality living may compromise due to sole earning
Children become mentally unstable by living alternatively with parents (in divorced cases).

3). Extended Family: Basically extended families are joint families, in which grandparents, parents and children live together to support each other both financially and socially.

Pros of extended family:

More tolerance level among children
Care and Respects for people older in age is practiced
Have emotional support
Have social support

Cons of extended family:

Face more financial crises due to large number of members in a family
Intervening in personal matters with each other
Low privacy

4).Childless Family: Partners who have no any children either by choice or due to infertility.

Pros of childless family:

More financially strong
No one to take care of
More free to do basic thing like travelling, shopping and fun activities
Have more chance to fulfill desired goal

Cons of childless family:

Develop fear of isolation by the time
Society pressure (not having kids)
Develop sense of lacking something important (infertile couples)

5). Step family:

When two families start living to gather, like two divorced people get married and living together with their children (from 1st partner).

Pros of step family:

Child gets advantage by living with both parents
Financially stable due to two source of incomes

Cons of step family:

Feeling of living forcefully with second parent
Couple fight often due to each other's children conflict
children develop leas tolerance

6) Grandparent Family: In which grandchildren are raised by their grandparents.

Pros of grandparent family:

Children have strong relationship with their elderly
More protective environment for children

Cons of grandparent family:

Less financially table
Difficult to raise children due to old age and related health issue
Big age gap

Similarities and Differences:

By considering the pros and cons of different family structure we come to the point that many of them have some similarities like financial stability, strong bonding, and more socialization. Likewise there are few differences as well as some families share strong bond while other suffers from isolation. Some are more financially stable and others are less. Some have children while other are childless. Some children have both parents while other have single or step patent. Some of them have high tolerance while other has less. Some live quality life whiles other compromise on their needs and wants.

7 0

3 years ago