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Lilit [14]
4 years ago
9

Janet ran 30 meters in 4 seconds,what is her speed.

Physics
2 answers:
lubasha [3.4K]4 years ago
8 0

Answer:

7.5 meters per second

Explanation:

30 / 4 = 7.5

7.5 * 1 = 7.5

7.5 * 2 = 15

7.5 * 3 = 22.5

7.5 * 4 = 30

MrRa [10]4 years ago
5 0

7.5 i believe it's right.

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and an ideal spring of unknown force constant. The oscillator is found to have a period of 0.157 s and a maximum speed of 2 m/s
DENIUS [597]

Answer:

k = 1073.09 N/m

A = 0.05 m

Explanation:

Given:

- Time period T = 0.147 s

- maximum speed V_max = 2 m/s

- mass of the block m = 0.67 kg

Find:

- The spring constant k

- The amplitude of the motion A.

Solution:

- A general simple harmonic motion is modeled by:

                                     x (t) = A*sin(w*t)

- The velocity of the above modeled SHM is:

                                     v = dx / dt

                                     v(t) = A*w*cos(w*t)

- Where A is the amplitude in meters, w is the angular speed rad/s and time t is in seconds.

- We can see that maximum velocity occurs when (cos(w*t)) maximizes i.e it is equal to 1 or -1. Hence,

-                                      V_max = A*w

- Where w is related to mass of the object and spring constant k as follows,

                                       w = sqrt ( k / m )

- The relationship between w angular speed and Time period T is:

                                       w = 2*pi / T

- Equating the above two equations we have,

                                        m*(2*pi / T)^2 = k

- Hence,                           k = 0.67*(2*pi / 0.157)^2

                                        k = 1073.09 N / m

- So, amplitude A is:

                                        A = V_max*sqrt ( m / k )

                                        A = 2*sqrt ( 0.67 / 1073.09 )

                                        A = 0.05 m      

6 0
4 years ago
In an experiment different wavelengths of light, all able to eject photoelectrons, shine on a freshly prepared (oxide-free) zinc
topjm [15]

Answer:

the energy of the photons is greater than the work function of the zinc oxide.

                     h f> = Ф

Explanation:

In this experiment on the photoelectric effect, it is explained by the Einstein relation that considers the light beam formed by discrete energy packages.

                    K_max = h f - Ф

in the exercise phase, they indicate that different wavelengths can inject electrons, so the energy of the photons is greater than the work function of the zinc oxide.

                     h f > = Ф

6 0
4 years ago
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