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3 years ago

10

Mechanical energy is a term that is used to describe A. kinetic energy only. B. both potential and kinetic energy. C. potential

energy only. D. neither potential nor kinetic energy.

2 answers:

gayaneshka [121]3 years ago

7 0

B. both potential and kinetic energy

myrzilka [38]3 years ago

5 0

Answer: B. both potential and kinetic energy.

Explanation:

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Initially, a 2.00-kg mass is whirling at the end of a string (in a circular path of radius 0.750 m) on a horizontal frictionless

drek231 [11]

Answer:

$v_f = 15 \frac{m}{s}$

Explanation:

We can solve this problem using conservation of angular momentum.

The angular momentum $\vec{L}$ is

$\vec{L} = \vec{r} \times \vec{p}$

where $\vec{r}$ is the position and $\vec{p}$ the linear momentum.

We also know that the torque is

$\vec{\tau} = \frac{d\vec{L}}{dt} = \frac{d}{dt} ( \vec{r} \times \vec{p} )$

$\vec{\tau} = \frac{d}{dt} \vec{r} \times \vec{p} + \vec{r} \times \frac{d}{dt} \vec{p}$

$\vec{\tau} = \vec{v} \times \vec{p} + \vec{r} \times \vec{F}$

but, as the linear momentum is $\vec{p} = m \vec{v}$ this means that is parallel to the velocity, and the first term must equal zero

$\vec{v} \times \vec{p}=0$

so

$\vec{\tau} = \vec{r} \times \vec{F}$

But, as the only horizontal force is the tension of the string, the force must be parallel to the vector position measured from the vertical rod, so

$\vec{\tau}_{rod} = 0$

this means, for the angular momentum measure from the rod:

$\frac{d\vec{L}_{rod}}{dt} = 0$

that means :

$\vec{L}_{rod} = constant$

So, the magnitude of initial angular momentum is :

$| \vec{L}_{rod_i} | = |\vec{r}_i||\vec{p}_i| cos(\theta)$

but the angle is 90°, so:

$| \vec{L}_{rod_i} | = |\vec{r}_i||\vec{p}_i|$

$| \vec{L}_{rod_i} | = r_i * m * v_i$

We know that the distance to the rod is 0.750 m, the mass 2.00 kg and the speed 5 m/s, so:

$| \vec{L}_{rod_i} | = 0.750 \ m \ 2.00 \ kg \ 5 \ \frac{m}{s}$

$| \vec{L}_{rod_i} | = 7.5 \frac{kg m^2}{s}$

For our final angular momentum we have:

$| \vec{L}_{rod_f} | = r_f * m * v_f$

and the radius is 0.250 m and the mass is 2.00 kg

$| \vec{L}_{rod_f} | = 0.250 m * 2.00 kg * v_f$

but, as the angular momentum is constant, this must be equal to the initial angular momentum

$7.5 \frac{kg m^2}{s} = 0.250 m * 2.00 kg * v_f$

$v_f = \frac{7.5 \frac{kg m^2}{s}}{ 0.250 m * 2.00 kg}$

$v_f = 15 \frac{m}{s}$

8 0

3 years ago

K donates, or transfers, one electron to bromine, which has 7 electrons. Both K and Br are now stable with 8 electrons. K become

Charra [1.4K]

K is cation by losing of electron whereas Br is anion due to accepting of electrons.

<h3 /><h3>Is charge appears when an atom lose or accept electron?</h3>

Yes, the positive ion appears on K and become cation whereas the negative ion bears on Br which make it anion because of losing and gaining of electron by these atoms. This transferring of electrons leads to formation of ionic bonds between them.

So we can conclude that K is cation by losing of electron whereas Br is anion due to accepting of electrons.

Learn more about ionic bond here: brainly.com/question/2687188

#SPJ1

4 0

2 years ago

A hockey puck has a mass of 0.107 kg and is at rest. A hockey player makes a shot, exerting a constant force of 28.0 N on the pu

gregori [183]

Answer:

The speed does it head toward the goal = 41.87 $\frac{m}{s}$

Explanation:

Mass = 0.107 kg

Initial velocity ( u ) = 0

Force (F) = 28 N

Time = 0.16 sec

From newton's second law, Force = mass × acceleration

⇒ F = m × a

⇒ 28 = 0.107 × a

⇒ a = 261.7 $\frac{m}{s^{2} }$ --------- (1)

This is the value of acceleration.

Final speed of the mass is calculated by the equation V = U + at

⇒ U = 0 because mass in in rest position at start.

⇒ V = a t

Put the values of acceleration and time in above formula we get

⇒ V = 261.7 × 0.16

⇒ V = 41.87 $\frac{m}{s}$

Therefore the speed does it head toward the goal = 41.87 $\frac{m}{s}$

5 0

3 years ago

The number of electromagnetic waves that travel past a certain point in a given time is the ________ of the radiation.

Rina8888 [55]

The period of the radiation?

8 0

3 years ago

A 380-N girl walks down a flight of stairs so that she is 2.5 m below her starting level. What is the change in the girl's gravi

Svetach [21]

PEg = Mass x Height x Gravity. So it doesn't matter how much PEg she started with, since you're finding how much it changed when she walked down 2.5 meters of stairs. So by plugging into the equation, you'll find how much potential energy was lost by walking down. (I'll leave it up to you since idk if you use 10 or 9.8 as gravity)

8 0

3 years ago

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