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3 years ago

A disk of radius 25 cm spinning at a rate of 30 rpm slows to a stop over 3 seconds. what is the angular acceleration?

Physics

1 answer:

SCORPION-xisa [38]3 years ago

5 0

Answer:

α = -π/3 rad/s²

θ = 1.5π rad ≈ 4.71 rad

θ = 0.75 rev

Explanation:

30 rev/min (2π rad/rev) / (60 s/min) = π rad/s

α = (ωf - ωi) / t = (0 - π) / 3 = -π/3 rad/s²

θ = ½αt² = ½(π/3)3² = 1.5π rad ≈ 4.71 rad

θ = 1.5π rad / 2π rad/rev = 0.75 rev

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A train travelling at 20 m/s has 2 000 000 J of kinetic energy. What is the mass of<br> the train?

Svetlanka [38]

Answer:

Explanation:

The mass of the train can be found by using the formula

$m = \frac{2k}{ {v}^{2} } \\$

k is the kinetic energy

v is the velocity

From the question we have

$m \frac{2(2000000)}{ {20}^{2} } = \frac{4000000}{400} = \frac{40000}{4} \\$

We have the final answer as

Hope this helps you

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3 years ago

Read 2 more answers

Radio waves travel 300,000,000 m/s. The frequency is 101,700,000. ehats the wavelength

Nesterboy [21]

Answer:

we have formula of frequency :

frequency(f)= speed of sound(c)/wavelength(λ)

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3 years ago

The density of a certain type of plastic is 0.75 g/cm3 . If a sheet of this plastic is 10.0 m long, 1.0 m wide, and 1 cm thick,

Oksanka [162]

Answer:

7.5 g

Explanation:

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3 years ago

A ray of white light moves through the air and strikes the surface of water in a beaker. The index of refraction of the water is

Naily [24]

Answer:

except ii and iii

Explanation:

The angle of reflection is the angle to the normal the white rays strikes the water surface and it is the incidence angle. Since the white light is moving from less dense medium to a denser medium or a medium with a higher refractive index; the angle of refraction will be less than 30 degrees. Total internal reflection cannot occur because the white light is traveling from a less dense medium to a denser medium.

3 0

3 years ago

an athlete in a hammer-throw event swings a 7.0-kilogram hammer in a horizontal circle at a constant speed of 12 meters per seco

Semenov [28]

Answer:

ac = 72 m/s²

Fc = 504 N

Explanation:

We can find the centripetal acceleration of the hammer by using the following formula:

$a_c = \frac{v^2}{r}$

where,

ac = centripetal acceleration = ?

v = constant speed = 12 m/s

r = radius = 2 m

Therefore,

$a_c = \frac{(12\ m/s)^2}{2\ m}$

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Now, the centripetal force applied by the athlete on the hammer will be:

$F_c = ma_c\\F_c = (7\ kg)(72\ m/s^2)$

6 0

2 years ago