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3 years ago

NEED ANSWER ASAP PLEASE!!!!!!!

Physics

1 answer:

Usimov [2.4K]3 years ago

7 0

In both questions, the objects are falling from rest so their final velocities after time $t$ will be given by

$v_f=v_i+at=at$

where $a$ is the acceleration due to gravity given. Note that I take the downward direction to be positive.

23.

$v_f=\left(9.8\,\dfrac{\mathrm m}{\mathrm s^2}\right)(7\,\mathrm s)\implies v_f=68.6\,\dfrac{\mathrm m}{\mathrm s}$

24.

$49\,\dfrac{\mathrm m}{\mathrm s}=\left(9.8\,\dfrac{\mathrm m}{\mathrm s^2}\right)t\implies t=5.0\,\mathrm s$

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Within a period of the periodic table, how do the properties of the elements vary?

Nonamiya [84]

Answer:

Elements in the same period have the same number of electron shells; moving across a period (so progressing from group to group), elements gain electrons and protons and become less metallic. This arrangement reflects the periodic recurrence of similar properties as the atomic number increases.

Explanation:

The Periodic Table can predict the properties of new elements, because it organizes the elements according to their atomic numbers. ... They hope that the two nuclei at the centre of these atoms will fuse and form a heavier nucleus. When these heavy elements form, they are usually highly unstable.

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3 years ago

Recall from Chapter 1 that a watt is a unit of en- ergy per unit time, and one watt (W) is equal to one joule per second ( J·s–1

harkovskaia [24]

Answer:

Explanation:

The energy of a photon is given by the equation $E_p=h f$ , where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of $E_N=N h f$ .

We also know that frequency and wavelength are related by $f=\frac{c}{\lambda}$ , so we have $E_N=\frac{N h c}{\lambda}$ , where c is the <em>speed of light</em>.

We will want the number of photons, so we can write

$N=\frac{\lambda E_N}{h c}$

We need to know then how much energy do we have to calculate N. The equation of power is $P=E/t$ , so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be $E_N$ .

Putting this paragraph in equations:

$E_N=(\frac{4}{100})E=0.04Pt=(0.04)(100W)(1s)=4J$ .

And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:

$N=\frac{\lambda E_N}{h c}=\frac{(520 \times10^{-9}m) (4J)}{(6.626\times10^{-34}Js) (299792458m/s)}=1.047 \times10^{19}$

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3 years ago

A cannon is fired straight up into the air. If the cannon ball comes back down to the launch point in 5 seconds, what was the ma

Nana76 [90]

Answer:

30.63 m

Explanation:

From the question given above, the following data were obtained:

Total time (T) spent by the ball in air = 5 s

Maximum height (h) =.?

Next, we shall determine the time taken to reach the maximum height. This can be obtained as follow:

Total time (T) spent by the ball in air = 5 s

Time (t) taken to reach the maximum height =.?

T = 2t

5 = 2t

Divide both side by 2

t = 5/2

t = 2.5 s

Thus, the time (t) taken to reach the maximum height is 2.5 s

Finally, we shall determine the maximum height reached by the ball as follow:

Time (t) taken to reach the maximum height = 2.5 s

Acceleration due to gravity (g) = 9.8 m/s²

Maximum height (h) =.?

h = ½gt²

h = ½ × 9.8 × 2.5²

h = 4.9 × 6.25

h = 30.625 ≈ 30.63 m

Therefore, the maximum height reached by the cannon ball is 30.63 m

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3 years ago

which of the glass lenses above, when placed in air, will cause rays of light (parallel to the central axis) to converge?

777dan777 [17]

Convex lenses when placed in the air, will cause rays of light (parallel to the central axis) to converge.

Converging lenses, commonly referred to as convex lenses, have thicker centers and narrower upper and lower margins. The edges are outwardly curled. This lens has the ability to concentrate a beam of parallel light rays coming from the outside onto a spot on the opposite side of the lens.

The image created is referred to be a genuine image when it is inverted relative to the object. On a screen, this kind of image can be recorded. When the object is positioned at a point farther than one focal length from the lens, a converging lens creates a true image.

A virtual image is one that cannot be produced on a screen and is formed when the image is upright in relation to the object. When an item is positioned within one focal length of a converging lens, a virtual image is created. It creates an enlarged image of the object on the same side of the lens as the image. It serves as a magnifier.

Learn more about the convex lens here:

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1 year ago

A 1000 kg truck moving at 2.0 m/s runs into a concrete wall. It takes 0.5 s for the truck to completely stop. What is the magnit

guajiro [1.7K]

Answer:

Momentum is given by

. Impulse is the change of momentum,

and is also equal to force times time:

. Rearranging,

−

000

−

4000

Explanation:

Momentum before the collision is

2000

⋅

000

−

Assuming the truck comes to a complete halt, the momentum after the collision is

−

The change in momentum,

, is initial minus final

→

−

000

−

000

This is called the impulse:

. Impulse is also equal (check the units) to force times time:

We can rearrange this expression to make

the subject:

−

000

−

4000

The negative sign just means the force acting is in the opposite direction to the initial momentum.

(This will be the average force acting during the collision: collisions are chaotic so the force is unlikely to be constant.)

3 0

3 years ago