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const2013 [10]
3 years ago
15

A CD player rotates at a variable speed so that a laser can scan pits and lands on the disk’s bottom surface at a constant tange

ntial speed of 1.2 m/s. The disk has a moment of inertia of 1.2 x 10-4 kg m2and the music is first detected when the laser is located 15 mm from the disk’s center. Assuming the disk started from rest, find the work done by the motor during this start-up.
Physics
1 answer:
LekaFEV [45]3 years ago
6 0

Answer:

W = 0.384 J

Explanation:

Work and energy in the rotational movement are related

    W = ΔK = K_{f} - K₀

    W = ½ I w_{f}² - 1 /2 I w₀²

where W isthe work, I is the moment of inertia and w angular velocity

With the system part of the rest the initial angular speed is zero (w₀ = 0)

The angular and linear quantities are related

    v = w r

    w = v / r

Let's replace

    W = ½ I (v / r)²

Let's calculate

    W = ½  1.2 10⁻⁴ 1.2² / (1.5 10⁻²)²

    W = 0.384 J

    W = 38.4 J

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Given the data in the question;

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<h3>Velocity</h3>

velocity is simply the same as the speed at which a particle or object moves. It is the rate of change of position of an object or particle with respect to time. As expressed in the Third Equation of Motion:

v^2 = u^2 + 2gh

Where v is final velocity, u is initial velocity, h is its height or distance from ground and g is gravitational field strength.

To determine the speed of the brick as it hits the ground, we substitute our giving values into the expression above.

v^2 = u^2 + 2gh\\\\v^2 = 0 + ( 2\ *\ 10m/s^2\ *\ 15m)\\\\v^2 = 300m^2/s^2\\\\v = \sqrt{300m^2/s^2}\\ \\v = 17.32m/s

Therefore, the speed of the brick dropped by the builder as it hits the ground is 17.32m/s.

Learn more about equations of motion: brainly.com/question/18486505

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<h3>What is specific heat?</h3>

The specific heat is the amount of heat required to change the temperature by 1°C. It is denoted by C.

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