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4 years ago

A flywheel with a very low friction bearing takes 1.6 h to stopafter the motor power

Physics

1 answer:

Nina [5.8K]4 years ago

7 0

Answer:

(I). The initial rotation rate is 4.29 rad/s.

(II). The revolutions is 3932.

Explanation:

Given that,

Time = 1.6 h

Angular velocity = 41 rpm

(I). We need to calculate the initial rotation rate in rad/s

$\omega=41\ rev/m$

$\omega=\dfrac{41\times 2\pi}{60}\ rad/s$

$\omega=4.29\ rad/s$

(II). We need to calculate the revolutions

Using formula of revolutions

$\theta=\omega t$

$\theta=4.29\times1.6\times3600$

$\theta=24710\ rad$

$\theta=\dfrac{24710}{2\pi}$

$\theta=3932\ revolution$

Hence, (I). The initial rotation rate is 4.293 rad/s.

(II). The revolutions is 3932.

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a block of mas $ m $ = 4.8 kg slides head on into a spring of spring constant $ k $ = 430 N/m. When the block stops, it has

steposvetlana [31]

Answer:

See explanation below

Explanation:

The question is incomplete. The missing part of this question is the following:

<em>"While the block is in contact with the spring and being brought to rest, what are (a)the work done by the spring force and (b) the increase in thermal energy of the blockfloor system? (c) What is the blocks speed just as it reaches the spring?"</em>

<em />

According to this we need to calculate three values: Work, Thermal Energy and Speed of the block when it reaches the spring.

Let's do this by parts.

<u>a) Work done by the spring:</u>

In this case, we need to apply the following expression:

W = -1/2 kx² (1)

We know that k = 430 N/m, and x is the distance of compressed spring which is 5.8 cm (or 0.058 m). Replacing that into the expression:

W = -1/2 * 430 * (0.058)²

<u>b) Increase in thermal energy</u>

In this case we need to use the following expression:

ΔEt = Fk * x (2)

And Fk is the force of the kinetic energy which is:

Fk = μk * N (3)

Where μk is the coeffient of kinetic friction

N is the normal force which is the same as the weight, so:

N = mg (4)

Let's calculate first the Normal force (4), then Fk (3) and finally the chance in the thermal energy (2):

N = 4.8 * 9.8 = 47.04 N

Fk = 0.28 * 47.04 = 13.1712 N

Finally the Thermal energy:

ΔEt = 13.1712 * 0.058

<u>c) Block's speed reaching the spring</u>

As the block is just reaching the speed, the initial Work is 0. And the following expression will help us to get the speed:

V = √2Ki/m (5)

And Ki, which is the initial kinetic energy can be calculated with:

Ki = ΔU + ΔEt (6)

And ΔU is the same value of work calculated in part (a) but instead of being negative, it will be positive here. So replacing the data first in (6) and then in (5), we can calculate the speed:

Ki = 0.7233 + 0.7639 = 1.4872 J

Finally the speed:

V = √(2 * 1.4872) / 4.8

Hope this helps

7 0

3 years ago

Eight books, each 4.6 cm thick and of mass 1.8 kg, lie on a flat table. How much work work is required to stack them on top of o

pantera1 [17]

Answer:

529.92Newton Meters

Explanation:

Work=force x displacement

8books in total

force is 1.8kg

dispplacement is 4.6cm

times both units by 8 and u get

force - 14,4

displacement - 36.8

now times boht together and u get 529.92nm

3 0

2 years ago

What happens to the distance between interference fringes if the separation between two slits is increased?

kolezko [41]

Answer:

It will decrease

Explanation:

The double-slit interference equation, which gives us the position y of a maximum on the screen (measured relative to the central position), is

$y=\frac{n\lambda D}{d}$

where

n is the order of the maximum

D is the distance between the slits and the screen

$\lambda$ is the wavelength of the light

d is the separation between the two slits

From the formula, we see that y is inversely proportional to d: this means that if the separation between the slits is increased, the distance of each maximum from the central position (y) decreases, therefore the distance between the interference fringes will decrease.

3 0

3 years ago

Whenever one object exerts a force on another object, the second object exerts a force of the same magnitude on the first object

Naddik [55]

Answer:

Explanation:

Newton third law of motion state that action and reaction are equal and opposite

6 0

3 years ago

What is the difference between charging by contact and charging by induction in terms of electron transfer.

Veronika [31]

Answer:

the main difference between charging by contact and charging by induction is that in the first case, the two objects are touching, while in the second case, the two objects do not touch

Explanation:

There are three methods of charging an object:

- Charging by friction: this is done by rubbing an object against another object. An example is when a plastic rod is rubbed with a wool cloth. When this is done, electrons are transferred from the wool to the rod, so both objects remain charged at the end of the process

- Charging by contact: this is done by putting in contact a charged object with a neutral, conducting object. In this case, the charges are transferred from the charged object to the neutral object; at the end of the process, the neutral object will also have a net electric charge, so it will be also charged.

- Charging by induction: in this case, we take a charged object, and a neutral object, and we place the two objects close to each other, but without touching. Let's assume that the charged object is negatively charged: in this case, the positive charges in the neutral object are attracted towards the negative charges of the charged object, while the negative charges of the neutral object are repelled away. As a result, the positive and negative charges in the neutral object split apart. If the object is connected to the ground, then negative charges move away, so the neutral object will remain positively charged.

Therefore, the main difference between charging by contact and charging by induction is that in the first case, the two objects are touching, while in the second case, the two objects do not touch.

5 0

3 years ago