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IgorC [24]
2 years ago
10

A basketball rolls off a deck that is 3.2 m from the pavement. The basketball lands 0.75 m from the edge of the deck. How fast w

as the basketball rolling? Seema lists the given values in a chart and determines that the unknown value is vx.
given: value:
change in y 3.2m
ay -9.8 m/s2
change in x 0.75m

Which describes Seema’s error?

A. The y and x values are switched.
B. The unknown is , not vx.
C. The value for ay is not known.
D. The value of y should be –3.2 m.
Physics
2 answers:
Aneli [31]2 years ago
6 0
The table is almost perfect. BUT ... since she called ay negative, that means she's calling the upward direction positive-y and the downward direction negative-y. In that case, since the ball moves downward from the deck to the pavement, the change in y should be negative 3.2 m. Everything else in her table is fine. Choice-D is the good one.

Now, regarding the speed of the ball ...
How long does it take to fall 3.2 m ?
Use the formula. D = 1/2 g T^2 .

3.2 = 4.9 T^2.

T^2 = 3.2/4.9

T = √(3.2/4.9) = 0.808 second.

The ball hit the pavement 0.808 second after it rolled off the deck. So that's also the time it took to move the 0.75 m horizontally.

Speed = distance / time

Speed = 0.75 m / 0.808 second

Speed = 0.928 meter/second .
just olya [345]2 years ago
6 0

Answer:

D. The value of y should be –3.2 m.

Explanation:

We have to remember that when we are talking about free fall, or parabolic motion, we have two types of Y distance, positive and negative, positive for when the object is going up, and negative for when the object is going down, since the ball goes from 3.2m at the deck, to the ground those are -3.2 meters since the ball is loosing altitude. So Seema´s error is setting Change in Y as positive.

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<span>Storm cells in a squall line typically move from the southwest to the northeast, and as the mature cells in the northeast begin to die off, new ones are formed at the opposite end to advance the line. The air in the southwest corner has strong vertical updrafts that allow new cells to grow and develop into thunderstorms.</span>
7 0
2 years ago
A camera gives a proper exposure when set to a shutter speed of 1/250 s at f-number F8.0. The photographer wants to change the s
Oksana_A [137]

Answer:

F4.0

Explanation:

To obtain a shutter speed of 1/1000 s to avoid any blur motion the f-number should be changed to F4.0 because the light intensity goes up by a factor of 2 when the f-number is decreased by the square root of 2.

5 0
2 years ago
A radar used to detect the presence of aircraft receives a pulse that has reflected off an object 5 ✕ 10−5 s after it was transm
Sunny_sXe [5.5K]

Answer:

7500 m

Explanation:

The radar emits an electromagnetic wave that travels towards the object and then it is reflected back to the radar.

We can call L the distance between the radar and the object; this means that the electromagnetic wave travels twice this distance, so

d = 2L

In a time of

t=5\cdot 10^{-5}s

Electromagnetic waves travel in a vacuum at the speed of light, which is equal to

c=3.0\cdot 10^8 m/s

Since the electromagnetic wave travels with constant speed, we can use the equation for uniform motion ,so:

d=vt (1)

where

v=c=3.0\cdot 10^8 m/s

t=5\cdot 10^{-5}s

d=2L, where L is the distance between the radar and the object

Re-arranging eq(1) and substituting, we find L:

L=\frac{vt}{2}=\frac{(3.0\cdot 10^8)(5\cdot 10^{-5})}{2}=7500 m

7 0
2 years ago
An infinite sheet of charge is located in the y-z plane at x = 0 and has uniform charge denisity σ1 = 0.51 μC/m2. Another infini
NNADVOKAT [17]

Answer:

 E_total = 5.8 10⁴ N /C

Explanation:

In this problem they ask to find the electric field at two points, the electric field is a vector magnitude, so we can find the field for each charged shoah and add them vectorally at the point of interest.

To find the electric field of a charged conductive sheet, we can use the Gauss law,

        Ф = E. d S = q_{int} / ε₀

Let us use as a Gaussian surface a small cylinder, with the base parallel to the sheet, the electric field between the sheet and the normal one next to the cylinder has 90º, so its scalar product is zero, the electric field between the sheet and the base has An Angle of 0º, therefore the scalar product is reduced to the algebraic product.

Let's look for the electric field for plate 1

The total flow is the same for each face, as there are two sides of the cylinder

       2E A = q_{int} /ε₀

For the internal load we use the concept of surface density

      σ = q_{int1} / A

      q_{int1} = σ₁ A

Let's replace

       2E A = σ₁ A /ε₀

        E₁ = σ₁ / 2ε₀

For the other plate we have a field with a similar expression, but of negative sign

       E₂ = -σ₂ / 2ε₀

The total field is,

        E_total = σ₁ / 2ε₀ + σ₂ / 2ε₀

       E_total = (σ₁ + σ₂) / 2ε₀

Let us apply this expression to our case, when placing a sheet without electric charge, a charge is induced for each sheet, the plate 1 that has a positive charge the electric field is protruding to the right and the plate 2 that has a negative charge creates a incoming field, to the right, as the two fields have the same address add

           The conductive sheet in the middle pate undergoes an induced load that is created by the other two plates, but because the conductive plate the charges are mobile and are replaced.

       E_total = (0.51 +0.52) 10⁻⁶ / 2 8.85 10⁻¹²

       E_total = 5.8 10⁴ N /C

Note that the field is independent of the distance between the plates

4 0
2 years ago
Which combination of initial horizontal velocity, (vh) and initial vertical velocity, (vv) results in the greatest horizontal ra
Naya [18.7K]

If an object is projected with vertical speed given as

v_v

now the time of flight of the object that time in which it comes back on ground

\Delta y = v_v t + \frac{1}{2}(-g)t^2

now here we will have

0 = v_v t - \frac{1}{2}gt^2

t = \frac{2v_v}{g}

now the range of projectile is given as

R = horizontal\: speed \times time

R = v_h(\frac{2v_v}{g}

now here we know that

v_v = v_0 sin\theta

v_h = v_0 cos\theta

now the range is given as

R = \frac{2(vsin\theta)(vcos\theta)}{g}

R = \frac{v^2sin2\theta}{g}

now in order to have maximum range we can say

sin2\theta = 1

2\theta = 90^0

so we will have

\theta = 45 ^0

so now we can say

v_v = v_h = \frac{v_0}{\sqrt2}

so both speed must be same to have maximum horizontal range

8 0
2 years ago
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