Lợi ích của lực ma sát và cách làm tăng

Answers

Answer 1
Ma sát có lợi và cách tăng ma sát: Ma sát giữa bánh xe với mặt đường, giữa đế giày với mặt đất, ma sát khi ta cầm một vật là ma sát có lợi. Làm tăng ma sát bằng cách tăng áp lực, tăng độ nhám của mặt tiếp xúc ( cắt nhiều khía ở vỏ xe, đế giày, rải cát trên đường trơn)


Related Questions

Which of the following is a force?
1) inertia
2) friction
3) acceleration
4) velocity

Answers

Hi there!

[tex]\large\boxed{\text{Friction.}}[/tex]

We can go through each:

1) Inertia is NOT a force. Inertia is defined as an object's resistance to motion, or its mass.

2) Friction IS a force because it results in acceleration.

3) Acceleration is not a force, but rather a product of force.

4) Velocity is simply a quantity that can be changed as a result of a force.

what do you mean by frequency of sound is 50Hz​

Answers

Answer:

This means the source of sound vibrates 50 times in one second. Therefore, number of vibrations in 1 minute, i.e. in 60 seconds = 50 x 60 = 3000 times.

Explanation:

If someone were to be researching and studying similarities between our sun and a neighboring star, what kind of scientific investigation would they be conducting

Answers

Answer:

a

Explanation:

because there both in the solar system

There are billions of galaxies in the universe and each contains trillions of stars which are different in size, distance from the earth, brightness etc.When we scientifically investigate about this we can obtain the stars of similarity to sun in brightness and size.

What is galaxies?

Galaxies are a group of stars, dust and dark matter joined together by the force of gravitation. Three trillions of stars in each galaxies. Some stars forms a group of certain  size and shape and number also they are called constellations.

Sun is the closest star to earth. Thus sunlight is the major source of energy in earth. Sunlight reaches the earth surface within a time of 8 minute and 6 seconds.

The star which nearest to sun is named proximacentory which far from the earth and we can see it as spot of light in the sky. There are many more stars which are giants are more brighter than sun.

The brightness and luminosity is determined based on the distance from the earth. Which can be calculated in terms of light years. Each star has an age and length of life. After that the star may die still their light energy can be seen in sky because their light takes more years to reach here.

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what is cleaning agent​

Answers

Answer:

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, bad smells, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others.

Answer:

Cleaning agents are substances created for the purpose of cleaning surfaces from germs dirt fungus diseases etcetera.

Explanation:

A car approaches you at 50 km/h. A fly inside the car is flying toward the back of the car at 7 km/h. From your point of view by the side of the road, the fly is moving at ______________km/h. Group of answer choices 57

Answers

Answer:

43 km/h

Explanation:

If the car is going past you at 50 km/h, then all the objects inside appear to be going 50 km/h. The fly is flying 7km/h in the opposite direction, and would appear to be going 7 km/h slower. Therefore, as 50 - 7 is 43, the fly would appear to be going 43 km/h. Hope this helps :D

pls help me do these physic questions

Answers

Answer:

1 since it is meatl and sharp

2 since it is sharp and iron

A rock from a volcanic eruption is launched straight up into the air with no air resistance.
Which one of the following statements about the rock while it is in the air is correct? *
(0.5 Points)
On the way up, its acceleration is downward and its velocity is upward. At the highest point both its velocity
and acceleration are zero.
On the way down, both its velocity and acceleration are downward. At the highest point both its velocity and
acceleration are zero.
The acceleration is downward all points in the motion, except that the acceleration is zero at the highest
point.
The acceleration is downward at all points in the motion
Throughout the motion, the acceleration is downward, and the velocity is always in the same direction as the
acceleration

Answers

Answer:

D. The acceleration is downward at all points in the motion

Explanation:

:D

A 455 kg cannon fires a 21 kg cannonball at 26 m/s. If the cannon is on wheels, at what velocity does it move backward?

Answers

Answer:

A cannon ball of mass 4.0 kg is fired from a stationary 96 kg cannon at 120 m/s. Calculate the velocity of the cannon immediately after firing.

total momentum of cannon and cannon ball before = 0 kg m/s - because neither object is moving

total momentum of cannon and cannon ball after collision = 0 kg m/s - because momentum is conserved

Momentum of cannon ball after firing = 4.0 × 120 = 480 kg m/s.

Momentum of cannon after firing = -480 kg m/s (because it recoils in the opposite direction and 480 - 480 = 0 kg m/s, the total momentum after collision).

Rearrange p = m v to find v:

v = p/m

v = 480 divided by 96

v = 5.0 m/s

Note that the forward velocity of the cannon ball was given a positive value. The negative value for the cannon's velocity shows that it moved in the opposite direction.

A kitchen has a water supply, an electricity supply and electric lighting there are several electrical appliances in the kitchen including a toaster, akettle a clothes iron, a microwave oven and a dishwasher discuss three hazards of using electricity in this kitchen ?

Answers

The hazards of using electricity in this kitchen include the following below:

Risk of electric shocks: These electrical appliances use an electric source for their various functions in which electric current flows through them when

turned on. Exposure and contact of the naked wire with individuals will bring

about shock.

Risk of burns: The kitchen has various heating appliances such as toaster,

kettle,iron and oven which may result in burns if not carefully handled.

Risks of fire : The heat and electric current from these appliances can trigger a spark and fire which may raze down the building is also another hazard.

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A man on the moon with a mass of 90 kilograms weighs 146 newtons. The radius of the moon is 1.74 x 10^6
meters. Find the mass of the moon

equation- F= G m1 m2/ d^2

Answers

Answer:

7.36 × 10^22 kg

Explanation:

Answer:

D

Explanation:

compared to ultraviolet waves, the wavelength of infrared waves is

Answers

Answer:

Visible spectrum is considered to be:

4000-7000 Angstroms

400 -700 Microns

Ultraviolet is   <400 microns    causes sunburn, cellular damage

Infrared >700 microns      -heating, heat lamps, etc

how much heat is needed to warm .052kg of gold from 24 degrees celsius to 120 degreees celsius

Answers

Explanation:

i need answers to this problem

A box of mass 20 kg has a base of area 4 m2
. Calculate the pressure exerted by it on the ground. (Use 1
kg-f = 10 N)

Answers

[tex]\huge \bf༆ Answer ༄[/tex]

First, find the force exerted by the box.

[tex] \sf \: F = ma [/tex]

The required terms are :

m = mass = 20 kg

a = Acceleration due to gravity = 10 m/s²

Calculate the force : -

[tex] \sf \: F = 20 \times 10 [/tex]

[tex] \sf \: F = 200 \: N[/tex]

_____________________________________

Pressure can be calculated using this formula : -

[tex] \sf \: P = \dfrac {F }{A }[/tex]

The stated terms are :

P = pressure

F = force = 200 N

A = Area = 4 m²

Calculate the Pressure now : -

[tex] \sf \: P = \dfrac{200}{4} [/tex]

[tex] \sf \: P = 50 \: pascals[/tex]

[tex]꧁  \:  \large \frak{Eternal \:  Being } \: ꧂[/tex]

Select the correct answer.
When rocks containing copper are oxidized, they tend to turn from red to green. Based on this information, what evidence
would best support the theory that oxidation could not have occurred in Earth's early atmosphere?
Rocks from early Earth that contained copper are green in color.
There are no copper-containing rocks from early Earth.
Rocks from early Earth that contained copper are red in color.
All copper minerals were converted to iron minerals.

Answers

Answer:

Rocks from early Earth that contained copper are red in color

Explanation:

"Copper, a red mineral, reacts with oxygen to form a green-colored compound. In early years, rocks containing copper were red. This fact shows that there was no oxygen in the early atmosphere to oxidize red copper into the green-colored compound."

Explain the relationship between the frequency, energy, and wavelength of a wave.​

Answers

Answer:

Explanation:

The energy equation is E=hv

Two illustrations labeled A and B. In Illustration A a hand is pushing on a mass labeled m that is connected to a spring and the spring is connected to a wall. In illustration B the spring is back to its normal length and the mass is moving away from the end of the spring at a velocity v. The position where the block started from is labeled x = 0. A spring attached to a mass is at rest in the initial position (not shown). The spring is compressed in position A and is then released, as shown in position B. Which equation describes conservation of energy in position A?

Answers

Answer:

The answer is (C) E= 1/2 kx^2

Explanation:

Answer:

ITS C JUST FINISH

Explanation:

A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned off and coasts to a stop in an additional 40 s. In the one minute of rotation, through how many revolutions did the fan turn?.

Answers

Hi there!

We can first find the angular displacement of the first 20 seconds by finding the angular acceleration.

Begin by converting 120 rev/min to rev/sec:

120 rev/min × 1 min/60 sec = 2 rev/sec

ω = αt

2 = 20α

α = 0.1 rev/sec²

θ = ωit + 1/2αt²

The fan starts from rest, so:

θ = 1/2αt²

θ = 1/2(0.1)(20²) = 20 revolutions

Now, for the next 40 seconds, we can find the fan's deceleration:

ωf = ωi + αt

0 = 2 + αt

-2 = 40α

α = -0.05 rad/sec²

Use the above equation:

θ = ωit + 1/2αt²

θ = 2(40) + 1/2(-0.05)(40²) = 80 - 40 = 40 rev

θ = 4800 - 2400 = 2400 revolutions

Add the two:

θtotal = 20 + 40 = 60 revolutions

The weight of a 1,000 kg car is ______________ (pick best answer)

Group of answer choices

9800 N

102.4 N

1000 N

10000 N​

Answers

What is the weight of a car with the mass of 1000 kg?

Answer: it is 9800 N.

On some strange planet you find that a 17.4 kg object falls downward 28.8 meters in 5.5 seconds. What is the magnitude of the acceleration due to gravity on this planet

Answers

Hi there!

[tex]\large\boxed{g = 1.904 m/s^2}[/tex]

Acceleration of gravity is unaffected by an object's mass.

In the absence of air resistance, we can use the following kinematic equation:

d = vit + 1/2at²

The object falls from rest, so:

d = 1/2at²

The acceleration in this instance is gravity, our unknown. We can rearrange the equation to solve for 'g':

2d/t² = g

2(28.8)/(5.5²) = 1.904 m/s²

A 45 kg object has a momentum of 255 kg m/s northward.What is the objects velocity​

Answers

Answer:

5.66 m/s

Explanation:

p=mv

255 = 45v

v = 255/45

v = 5.66 m/s

If you want to verify your answer, just insert your value to the equation.

Why does time seem to flow only in one direction? ...​

Answers

Answer:

Mass is relative too. Thus, as much fuel as you pack you will never reach the velocity of light. At the velocity of light, if you were somehow to reach it, your mass will be infinite and it will so require infinite force to push you, so no going beyond that speed. This is the reason time flows in a single direction.

Explanation:

Managers use information systems to help them make decisions that will improve their businesses. What three levels of information do managers need to make these decisions? Provide one example of how information systems can provide this data.

Answers

The main categories of information systems include management-level system, operational-level system, and strategic-level system.

Information system simply means the integrated set of components that are vital for the collection, storage, and processing of data to make organizational decisions.

Information systems can be used at operational level in order to provide data that can support operational activities by keeping track of the transactions of the company.

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Which of the following, if eliminated, would completely prevent the greenhouse effect from occurring on earth?

A. Atmosphere Clouds

B. Fossil fuels

C. Acid rain

D. The ozone layer

E. Chlorofluorocarbons​

Answers

I think answer correct A ……………

Chlorofluorocarbons​ is eliminated, would completely prevent the greenhouse effect from occurring on earth.

What is greenhouse effect?

The greenhouse effect is a phenomenon in which heat from a planet's host star passes through its atmosphere and warms the surface of the planet, but greenhouse gases in the atmosphere prevent part of the heat from going directly to space, making the world warmer.

Chlorofluorocarbons gas is main cause of greenhouse effect so when we remove it from atmosphere than green house effect will be reduced.

Chlorofluorocarbons​ is eliminated, would completely prevent the greenhouse effect from occurring on earth.

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A bus speeds up from 5 m/s to 15 m/s in 20 seconds. How far did it go during the 20 seconds? (use KE1 to find a, then use that to find xf)

Answers

The distance the bus travelled in 20 seconds is 12.75 m

The first step is to write out parameters given in the question

Final velocity= 15

Initial velocity= 5

Time= 20

Distance= ?

V² + U²= 2as

15² + 5²= 2(9.8)s

225+25= 19.6s

250= 19.6s

s= 250/19.6

= 12.75

Hence the distance the bus travelled in 20 seconds is 12.75 m

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What is the use of a hydrometer​

Answers

Answer:

A hydrometer is an instrument used to determine specific gravity

Answer:

it is used determine specific gravity

Explanation:

and u can see them in use by measuring proof of moonshine

Which sense is used to determine whether an object is something you might want to eat?

smell

sight

taste

all of the above

Answers

Answer: D, All of the above!

Explanation:

I just helped my daughter with this test and it was correct!! Good luck !!

According to the principle of regularity, it is recommended that an individual exercise.

A 3-4 days per week at the beginning and progress to 4 or 5 days a week as your fitness improves.

B 7 days per week at the beginning and progress to 4 or 5 days a week as your fitness improves.

C 3-4 days per week at the beginning and progress to 7 days a week as your fitness improves.

D 1-2 days per week at the beginning and progress to 5 or 6 days a week as your fitness improves.

Answers

Answer:

Socratic app

Explanation:

it will help you

this painting represents the milky way galaxy as it would appear edge-on from a distance. label the indicated features; be sure to pay attention to where the leader lines are pointing.

Answers

The galaxy is known to contain stars of different ages. The indicated features as it points  from left to right are;

globular clusters bulge halo

Bottom row

Both are disks

The Milky Way Milky exist because  our Sun (a star) and all the planets close to it are part of a galaxy called the Milky Way Galaxy.

A galaxy is known to be a large group of stars, gas, and dust bound together by the force of gravity.

Our galaxy is called by the name the Milky Way because it is usually seen or it appears as a milky band of light in the sky when you view it in a really dark area.

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when calculating the binding energy, what is z multiplied by?

Answers

Z times the mass of a hydrogen atom.

When calculating the binding energy, z multiplied by the sum of mass of proton and mass of electron.

What is z in binding energy?

Z in binding energy calaculation is the number of protons in the nuclides.

Formula for binding energy

To calculate the binding energy we use the formula below;

E = Z (mp + me) + Nmn − mn

Where;

Z is the number of protons in the nuclides N is the number of neutronsmp is mass of protonme is mass of electron

Thus, when calculating the binding energy, z multiplied by the sum of mass of proton and mass of electron.

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6. Two skaters, Jim (65 kg) and Mary (50 kg) are standing at rest on the ice. They push each other
and Mary recedes at 2.5 m/s towards the east. Find Jim's velocity (magnitude and direction).

Answers

Hi there!

This is an example of a recoil collision.

Let m1, v1 be Mary

Let m2, v2 be Jim

Utilize the conservation of momentum:

m1v1 + m2v2 = m1v1' + m2v2'

The initial velocities are zero (at rest), so:

0 = m1v1' + m2v2'

Let east be positive, so Jim recoils with a negative velocity:

0 = m1v1' - m2v2'

Set the two equal and solve:

m1v1' = m2v2'

m1v1'/m2 = v2'

(50)(2.5)/65 = v2' = 1.92 m/s to the WEST

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