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3 years ago

Using the law of conservation of energy, what will be the KE of an arrow having a PE of 65J after it is shot from a bow?

Physics

1 answer:

Colt1911 [192]3 years ago

7 0

Answer:

KE = 65 J (The potential energy stored in the stretched bow is converted to kinetic energy of the moving bow)

Explanation:

Law of conservation of energy states that energy can neither be created nor be destroyed but transferred from one form to another. In other words, the total energy of the system at any point is always a constant.

Now, when the bow is in stretched position, the energy associated with the stretched bow is potential energy (PE).

The energy associated with motion of the body is kinetic energy (KE).

So, the stretched bow is not moving. So, KE at the start is 0.

Therefore, total energy initially is given as:

Initial total energy = PE + KE = PE + 0 = 65 J

Now, when the bow is shot, the bow is in motion. So, the total energy of the bow is only due to kinetic energy associated with it now. Also, the potential energy of a moving bow is 0.

Therefore, final total energy is given as:

Final total energy = Final KE + Final PE = Final KE + 0 = Final KE

Now, we know, from conservation of energy,

Initial total energy = Final total energy

⇒ 65 J = KE

or Final KE = 65 J

Therefore, the KE of an arrow having a PE of 65J after it is shot from a bow is 65 J.

Hence, the potential energy stored in the stretched bow is converted to kinetic energy of the moving bow.

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An electron has a kinetic energy of 3.00 ev. find its wavelength. (b) what if? a photon has energy 3.00 ev. find its wavelength.

Harman [31]

(a) The electron kinetic energy is
$K=3.00 eV$
which can be converted into Joule by keeping in mind that
$1 eV=1.6 \cdot 10^{-19}eV$
So that we find
$K=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The kinetic energy of the electron is related to its momentum p by:
$K= \frac{p^2}{2m}$
where m is the electron mass. Re-arranging the equation, we find
$p= \sqrt{ 2Km}= \sqrt{ 2 ( 4.8 \cdot 10^{-19} J)(9.1 \cdot 10^{-31} kg) } =9.35 \cdot 10^{-25} kgm/s$

And now we can use De Broglie's relationship to find its wavelength:
$\lambda= \frac{h}{p}= \frac{6.6 \cdot 10^{-34} Js}{9.35 \cdot 10^{-25} kg m/s} =7.06 \cdot 10^{-10}m$
where h is the Planck constant.

(b) By using the same procedure of part (a), we can convert the photon energy into Joules:
$E=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The energy of a photon is related to its frequency f by:
$E=hf$
where h is the Planck constant. Re-arranging the equation, we find
$f= \frac{E}{h}= \frac{4.8 \cdot 10^{-19} J}{6.6 \cdot 10^{-34}Js} =7.27 \cdot 10^{14}Hz$

And now we can use the relationship between frequency f, speed of light c and wavelength $\lambda$ of a photon, to find its wavelength:
$\lambda= \frac{c}{f}= \frac{3 \cdot 10^8 m/s}{7.27 \cdot 10^{14} Hz} =4.13 \cdot 10^{-7} m$

8 0

3 years ago

Idaho Jo is doing physics experiments throughout the solar system. She travels to each planet and shoots a potato straight up in

Natalka [10]

Answer:

Mercury / Mars

Explanation:

For an object launched straight upward, the following SUVAT equation can be used

$v^2-u^2=-2gh$

where

v is the final velocity

u is the initial velocity

g is the acceleration of gravity (free fall acceleration) (the negative sign is due to the downward direction of gravity)

h is the maximum height reached

At the maximum height, the velocity is zero, so v = 0. Re-arranging the equation,

$h=\frac{u^2}{2g}$

So we see that for equal initial velocity (u), the maximum height reaches is inversely proportional to the acceleration of gravity. Therefore, the potato gun will reach the highest altitude in the planets with lowest acceleration of gravity, therefore Mercury and Mars (3.7 and 3.6 m/s^2).

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3 years ago

True or False: Inertia is the property that every material object has that causes objects to resist changes in its state of moti

goldfiish [28.3K]

That is True because if it resists it means to not do it and if it is motion, that means that it is resisting movement and that is what inertia is.

The scientific definition for inertia is: "a tendency to do nothing or to remain unchanged"
Glad to help. :)

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3 years ago

The passengers are facing forward in the direction that the train is moving. What will happen to the passengers sitting on a tra

marysya [2.9K]

Passengers which are facing forward in the direction that train is moving, their bodies will move forward in application of sudden stop of train.

<h3>What is force of inertia?</h3>

Force of inertia is the force which acts in the opposite direction of the force of acceleration acting on the body.

Given infroamtion-

The passengers are facing forward in the direction that the train is moving.

The train comes to a sudden stop.

Lets see what happens step wise-

Here, the train in moving in the forward direction and the passengers are also facing forward in the direction that the train is moving.

Now the train comes to a sudden stop. By this sudden stop the train stops suddenly but all the object including the passengers is still travelling forward due to the inertia force.

Thus all the passenger will tend to move in the direction as they are still travelling.

Hence, passengers which are facing forward in the direction that train is moving, their bodies will move forward in application of sudden stop of train.

Learn more about the force of inertia here;

brainly.com/question/10454047

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2 years ago

PLEASE HELP!!!!!!!! More science questions coming soon!!

Naily [24]

Answer:

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So let's make oxygen 2 atoms at LHS by adding 2 to water molecules and hydrogen molecules at the RHS.

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The correct answer is A - 1,2,1,2

2.) Both magnetic force and gravitational force obey inverse square law with distance. They are not directly proportional but inversely proportional to the square distance. B is the correct answer because Both forces can act without objects touching.

3.) Light waves are transverse waves which can travel through a vacuum without a medium while sound waves are longitudinal waves which cannot travel through vacuum without a medium. But both can be modeled as waves having amplitude, frequency and wave lengths.

4.) If an object is slowing down, due to conservation of energy,

The potential energy could be increasing, like a ball thrown into the air.

The kinetic energy could be lost to friction or air resistance.

The ball could be returning to its natural resting state.

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3 years ago