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e-lub [12.9K]
3 years ago
5

During a hard drive crash the read/write head scrapes against the disk with a coefficient of kinetic friction of µk and normal f

orce of N. Assume that just before the head crash the disk is rotating at ω0 rad/s, and the distance of the head from the disk axis is r. You can ignore any friction at the bearing (rotational axis of the disk). Assume that the disk is uniform, and has radius R and mass M. What is the angular acceleration associated with the torque from the crashed disk head?
Physics
1 answer:
Alex_Xolod [135]3 years ago
3 0

Answer:

 α = \frac{2 \mu \  N}{m \ r}

Explanation:

For this exercise we use Newton's equation for rotational motion

           ∑ τ = I α

the troque is

           α = Fr .r

the moment of inertia of a cylinder is

           I = ½ m r²

we substitute

         fr r = (½ m r²) α

the expression friction is

         fr = μ N

we substitute

         μ N r = ½ m r² α

       

         α = \frac{2 \mu \  N}{m \ r}

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Please help I don't know how to answer these questions!
Yuki888 [10]

1) The potential energy is the most at the highest position and the least at the equilibrium position

2) The kinetic energy is the most at the equilibrium position and  the least at the highest position

Explanation:

1)

The potential energy of an object is the energy possessed by the object due to its position in a gravitational field; mathematically, it is given by

PE=mgh

where

m is the mass of the object

g is the strength of the gravitational field

h is the height of the object relative to the ground

For the pendulum in this problem, m is the mass of the bob, and h is the height of the above relative to the ground. We see from the formula that the potential energy is directly proportional to the height:

PE\propto h

This means that:

  • The potential energy is the most when the bob is at the highest position
  • The potential energy is the least when the bob is at the equilibrium position,  which is the lowest position

2)

We can solve this part by applying the law of conservation of energy: in fact, the total mechanical energy of the pendulum (sum of potential and kinetic energy) is constant at any time during the motion,

E=KE+PE=const.

where KE is the kinetic energy.

From the equation above, we observe that:

  • When PE is maximum, KE must be at minimum
  • When PE is minimum, KE must be maximum

Therefore, this implies that:

  • The kinetic energy is the most when the potential energy is the least, i.e. at the equilibrium position
  • The kinetic energy is the least when the potential energy is the most, i.e. at the highest position

Learn more about kinetic and potential energy:

brainly.com/question/6536722

brainly.com/question/1198647

brainly.com/question/10770261

#LearnwithBrainly

6 0
3 years ago
I got the correct answer, but I don't know what I did. Why is the answer E?
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Explanation:

Displacement is the straight line distance from the starting position to the final position.

Person X walks halfway around circle.  So her displacement is 100 m.

Person Y walks 3/4 of the way around.  So his displacement is 50√2 m ≈ 70.7 m.

Person Z walks completely around the circle, so their displacement is 0 m.

Therefore:

Z < Y < X

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2 years ago
Paul lifts a sack weighing 245 newtons vertically from the ground and places it on a platform at a height of 0.7 meters. If he t
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Answer:

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Explanation:

Given that

Time = 10 seconds

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Power = work done/ time taken

Where work done = force × distance

Substituting the given parameters into the formula

Work done = 245 newton × 0.7 meters

Work done = 171.5 J

Recall,

Power = work done/time

Power = 171.5 J ÷ 10

Power = 17.15 watts

Hence the power expended is B. 17.15 watts

6 0
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An electroscope is a fork-shaped device commonly used to detect the presence of charge. The tin leaves of an electroscope will s
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Answer:

All these is caused by the repulsion force.

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The electroscope produces a series of electric charges that produce a repulsion force when is putted in contact with a electric charged object.

As the physics law mentions, two different forces are repealed, the electrocospe is charged negatively and the object positively, causing a repulsion force that avoids that both objects touch the other.

7 0
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