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2 years ago

Please help will mark brainliest

Physics

2 answers:

andreyandreev [35.5K]2 years ago

7 0

Answer:

Explanation:

it melts yes but it's still water [same element] so there fore it's a physical change

Zolol [24]2 years ago

5 0

Answer:

It does not change the chemical composition of water. Explanation: A physical reaction is defined as the reaction in which a change in shape, size takes place. No new substance gets formed in these reactions.

Explanation:

Hope this helped

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For an object producing a thermal spectrum, a higher temperature causes the spectrum to have ___________. a. a peak intensity lo

anzhelika [568]

Answer:

a. a peak intensity located at shorter wavelength

Explanation:

We can answer this question by using Wien's displacement law, which relates the temperature of a black body to the peak wavelength of the spectrum of its emitted radiation, as follows:

$\lambda_p T = b$

where:

$\lambda_p$ is the wavelength of the peak of its spectrum

T is the absolute temperature at the surface of the body

$b=2.898\cdot 10^{-3} m\cdot K$ is called Wien's constant

From the equation above, we see that the peak wavelength and the temperature have an inverse relationship. In fact, we can rewrite it as

$\lambda_p = \frac{b}{T}$

By looking at the equation in this form, we can see that the higher the temperature of the object, the shorter the wavelength of its peak: therefore, the correct answer is

a. a peak intensity located at shorter wavelength

4 0

3 years ago

Hey guys <3

Rus_ich [418]

Answer:

8/9 parts

Explanation:

mark me as brainliest

5 0

2 years ago

A motor has coils with a resistance of 10.0 ohms and is supplied by a voltage of V = 1.20 x 102 V. When the motor is running at

Vanyuwa [196]

Hi there!

a)
When the motor is first turned on, the coils are initially stationary. Thus, there is no change in magnetic flux and, consequently, no induced emf.

Therefore:
$iR = \epsilon - \epsilon_{back}$

Since there's no back emf:
$iR = \epsilon$

Solving for i using Ohm's Law:
$i = \frac{\epsilon}{R}\\\\i = \frac{120}{10} = \boxed{12.0 A}$

We are given that at max speed, the back EMF is 70.0 V.

Using the same equation as above:
$iR = \epsilon - \epsilon_{back}$

Plugging in the values:
$10i = 120 - 70 \\\\10i = 50 \\\\$

Solving for current:
$i = \frac{50}{10} = \boxed{ 5.0 A}$

8 0

1 year ago

A cord of negligible mass runs around two massless, frictionless pulleys. A canister with mass m = 20 kg hangs from one pulley.

photoshop1234 [79]

(a) 196 N

The equation of the forces on the side of the cord where the force F is applied is:

$F-T=0$ (1)

where T is the tension in the cord.

On the other side of the cord, the equation of the forces on the canister is

$T-mg = ma$ (2)

where

m = 20 kg is the mass of the canister

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

a is the acceleration

From (1),

$T=F$

Substituting into (2),

$F-mg = ma\\F=m(g+a)$

We want the canister to move at constant speed, so

a = 0

And therefore:

$F=mg=(20)(9.8)=196 N$

b) 2.0 cm

The cord is inextensible, this means that the acceleration of its parts are the same. Therefore, the acceleration of the free end must be the same as the acceleration of the canister: and this means that the two parts also cover the same distance in the same time.

Therefore, the free end of the cord must be moved exactly the same as the canister, by 2.0 cm.

c) 3.92 J, the same

The work done by the tension in the cord is

$W_T = T d$

where

T is the tension

d = 2.0 cm = 0.02 m is the displacement

As we said in part (a), the tension in the cord is equal to the force applied to the free end:

T = F

T = 196 N

Therefore, the work done by the tension is

$W=(196)(0.02)=3.92 J$

And since the force applied (F) is the same, then the work done by you when pulling the cord is exactly the same.

(d) -3.92 J

The weight of the canister is

$F_g = mg =(20 kg)(9.8 m/s^2)=196 N$

However, the direction of the force of gravity is opposite to the displacement. Therefore, the work done by gravity is negative:

$W_g = - F_g d$

And substituting,

$W_g=-(196)(0.02)=-3.92 J$

(e) Zero

The net work done on the canister can be simply calculated by adding the work done by the tension in the cord and the weight of the canister:

$W=W_T+W_g = 3.92 + (-3.92 ) = 0$

This is in agreement with the work-energy theorem, which states that the work done on an object is equal to its change in kinetic energy. In this situation, the canister is moving at constant speed, so its kinetic energy is not change: therefore,

$\Delta K = 0$ (change in kinetic energy = 0)

and so, the work done on it is also zero.

(f) The pulley system changes the direction of the force applied

This is a simple pulley system, which means that the system does not multiply the force applied in input. In fact, the mechanical advantage of the system is

$MA=\frac{F_{out}}{F_{in}}$

where:

$F_{out}$ is the output force, which is the weight of the canister

$F_{in}$ is the force in input, which is F

So, the mechanical advantage is 1:

$MA=\frac{196 N}{196 N}=1$

From a point of view of energy, therefore, there is no advantage in this system.

However, the advantage offered by the pulley system concerns the direction of the force: in fact, it changes the direction of the applied force (which is F, downward) into the tension of the cord (which is upward on the canister).

6 0

3 years ago

What holds the moon in place, orbiting around earth?

pshichka [43]

Answer:

Gravity

Explanation:

5 0

1 year ago

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