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4 years ago

If a stone has 390 J of energy and is moving with

Physics

1 answer:

algol [13]4 years ago

8 0

Answer:

5.4 g

Explanation:

The stone is already in motion, so the only energy it has is kinetic. The formula for kinetic energy is:

$KE=\frac{1}{2} mv^{2}$

You can substitute the 390 J in for KE and 12 m/s in for v. After that, the equation looks like:

$390=\frac{1}{2} m12^{2}$

Then do basic algebra and m=5.4 g

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Ferns that eject spores generally do so in pairs, with two spores flying off in opposite directions. The structure from which th

Furkat [3]

Answer:

It cancels recoil.

Explanation:

For each action there is an equal an opposite reaction.

The principle of conservation of momentum tell us that if a single spore were ejected the fern would suffer a recoil from it. This recoil would take energy and speed from the spore. But if they are ejected in pairs the recoil is canceled and all the energy is transferred to the spores resulting in higher speeds.

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4 years ago

Which accurately describes the behavior of sound and light in the vacuum of space?

Romashka-Z-Leto [24]

A vacuum doesn't contain a medium. Light, which is an electromagnetic
wave and doesn't require a medium, will travel there. Sound, which is a
mechanical wave and requires a medium, will not travel there.

(You can see the light of the sun and other stars, which travels to us through
space. Astronauts can't hear the sound of each others' voices when they're
standing together on the moon because there's no medium between them,
so they have to use radio even to go only a few feet.)

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4 years ago

Read 2 more answers

A tank whose bottom is a mirror is filled with water to a depth of 20.0 cm. A small fish floats motionless 7.0 cm under the surf

liberstina [14]

Answer:

The apparent depth of (a) the fish is 5.3 cm and (b) the image of the fish is 24.8 cm.

Explanation:

According to the following equation:

$\frac{n_{w} }{s} +\frac{n_{a} }{s'} = \frac{n_{a}- n_{w}}{R_{c} } \\$

where nw and na is the refractive indices of water (1.33) and air (1.00) respectively; s is the depth of the fish below the surface of the water; s' is the apparent depth of the fish from normal incidence and Rc is the radius of curvature of the mirror at the bottom of the tank.

Note that the bottom of the tank is assumed to be a flat mirror, therefore the radius of curvature is very large (R⇒∞).

Therefore, the above equation can be expressed as:

$\frac{n_{w}}{s} +\frac{n_{a}}{s'}=0$

Now we can solve for the apparent depth of the fish.

(a) $s'=-(\frac{n_{a}}{n_{w}})x s$ (Make s' subject of the formula from the above equation)

$s'=(\frac{1.00}{1.33} )x7cm$

∴ $s'=5.3 cm.$

(b) The motionless fish floats 13 cm above the mirror, therefore the image of the fish will be situated at 13 + 20 =33 cm away from the real fish.

Therefore, s = 33 cm

$s'=-(\frac{n_{a}}{n_{w}})x s$

$s'=(\frac{1.00}{1.33} )x 33 cm$

$s'=24.8 cm.$

NB: Here, it is assumed that the water is pure, as impurities may alter the refractive index of water.

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4 years ago

A circuit has a current of 1.2 A. If the voltage decreases to one third of its original amount while the resistance remains cons

Katen [24]

When resistance is constant, current is proportional to voltage. When 1/3 the voltage is applied, 1/3 the current will result.

(1/3)*(1.2 A) = 0.4 A

The resulting current will be 0.4 A.

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3 years ago

What could result from regular participation in sports and exercise?

Sav [38]

A decrease in blood pressure. Next time please add the answer choices so people who want to answer your questions can do so!

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3 years ago