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Leviafan [203]
3 years ago
15

Two basketball players are essentially equal in all respects. (They are the same height, they jump with the same initial velocit

y, etc.) In particular, by jumping they can raise their centers of mass the same vertical distance, (called H their "vertical leap"). The first player, Arabella, wishes to shoot over the second player, Boris, and for this she needs to be as high above Boris as possible. Arabella jumps at time , and Boris jumps later, at time (his reaction time). Assume that Arabella has not yet reached her maximum height when Boris jumps.
1)Find the vertical displacement , D(t) = H(a)(t) - H(b)(t) as a function of time for the interval 0 < t < t(r) , where H(a)(t) is the height of the raised hands of Arabella, while H(b)(t) is the height of the raised hands of Boris.

Express the vertical displacement in terms of H, g , and t.
Physics
1 answer:
ser-zykov [4K]3 years ago
7 0
The reaction time of Boris is t(r), so before that, Boris will not have jumped. Thus, H(b)(t) = 0
The vertical displacement will simply be
D(t) = H(a)(t)
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Will two separate 50db sounds together constitute a 100db sound explain mathematical
vfiekz [6]
Putting together two distinct 50 dB sound, do not create a 100 dB sound. Since decibels are logarithm of energy, creating two sounds together only makes the energy increase but the logarithm only goes up by somehow little. So increasing the sound by 10 dB, only makes it 10000 times louder because each 10 dB increase in sound makes the sound 10 times louder.

Twice as loud is an increase of 10Log (2) = 3.01 dB. So, 53,01 dB is twice as loud as 50dB.
5 0
3 years ago
If a nearsighted person has a far point df that is 3.50 m from the eye, what is the focal length f1 of the contact lenses that t
Anastaziya [24]

Answer:

f1 = -3.50 m

Explanation:

For a nearsighted person an object at infinity must be made to  appear  to be at his far point which is 3.50 m away. The image of an object at infinity must be formed on the same side of the lens as the object.

∴ v = -3.5 m

Using mirror formula,

i/f1 = 1/v + 1/u

Where f1 = focal length of the contact lens, v = image distance = -3.5 m, u =         object distance = at infinity(∞) = 1/0

∴ 1/f1 = (1/-3.5) + 1/infinity

  Note that, 1/infinity = 1/(1/0) = 0/1 =0.

∴ 1/f1 = 1/(-3.5) + 0

  1/f1 = 1/(-3.5)

Solving the equation by finding the inverse of both side of the equation.

∴ f1 = -3.50 m

 Therefore a converging lens of focal length  f1 = -3.50 m

would be needed by the person to see an object at infinity clearly

8 0
3 years ago
Two very large parallel metal plates, separated by 0.20 m, are connected across a 12-V source of potential. An electron is relea
Semmy [17]

Answer:

{\rm K} = 2.4\times 10^{-19}~J

Explanation:

The electric field inside a parallel plate capacitor is

E = \frac{Q}{2\epsilon_0 A}

where A is the area of one of the plates, and Q is the charge on the capacitor.

The electric force on the electron is

F = qE = \frac{qQ}{2\epsilon_0 A}

where q is the charge of the electron.

By definition the capacitance of the capacitor is given by

C = \epsilon_0\frac{A}{d} = \frac{Q}{V}\\\frac{Q}{\epsilon_0 A} = \frac{V}{d} = \frac{12}{0.20} = 60

Plugging this identity into the force equation above gives

F = \frac{qQ}{2\epsilon_0 A} = \frac{q}{2}(\frac{Q}{\epsilon_0 A}) = \frac{q}{2}60 = 30q

The work done by this force is equal to change in kinetic energy.

W = Fx = (30q)(0.05) = 1.5q = K

The charge of the electron is 1.6 \times 10^{-19}

Therefore, the kinetic energy is 2.4\times 10^{-19}

8 0
3 years ago
4. Water is flowing at 12m/s in a horizontal pipe under a pressure of 600kpa
shusha [124]

Answer:

a. 192 m/s

b. -17,760 kPa

Explanation:

First let's write the flow rate of the liquid, using the following equation:

Q = A*v

Where Q is the flow rate, A is the cross section area of the pipe (A = pi * radius^2) and v is the speed of the liquid. The flow rate in both parts of the pipe (larger radius and smaller radius) needs to be the same, so we have:

a.

A1*v1 = A2*v2

pi * 0.02^2 * 12 = pi * 0.005^2 * v2

v2 = 0.02^2 * 12 / 0.005^2

v2 = 192 m/s

b.

To find the pressure of the other side, we need to use the Bernoulli equation: (600 kPa = 600000 N/m2)

P1 + d1*v1^2/2 = P2 + d1*v2^2/2

Where d1 is the density of the liquid (for water, we have d1 = 1000 kg/m3)

600000 + 1000*12^2/2 = P2 + 1000*192^2/2

P2 = 600000 + 72000 - 1000*192^2/2

P2 = -17760000 N/m2 = -17,760 kPa

The speed in the smaller part of the pipe is too high, the negative pressure in the second part means that the inicial pressure is not enough to maintain this output speed.

4 0
3 years ago
Four different observers are standing in a straight line on a street and hear a siren from a police car. Each person recorded th
Amanda [17]

Answer:

Wycleff is on block 1, Lilly is on block 4, Emilia is on block 12, and Quincy is on block 17.

Explanation:

Wycleff was at block 1 and heard a low pitch sound the whole time, so the police car must have been moving away from him.

Lilly observed was in block 4 change in pitch first.  So the car must have passed her first.

Emilia was at block 12 observed a Doppler effect after Lilly.  So the car passed her after passing Lilly

Quincy was at block 17 so she heard a high pitch sound the whole time, so the police car must have been moving toward him.

7 0
3 years ago
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