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Aloiza [94]
3 years ago
12

in the history of astronomy, which of the following is true? a. galileo galilei was a student of tycho brahe. b. johannes kepler

built one of the first observatories. c. ptolemy argued that earth was the center of the universe. d. isaac newton was criticized for his work on the geocentric model.
Physics
1 answer:
bija089 [108]3 years ago
7 0
C. Ptolemy argued that earth was the center of the universe
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A tradesman sharpens a knife by pushing it with a constant force against the rim of a grindstone. The 30-cm-diameter stone is sp
Lorico [155]

Answer:

a. 0.21 rad/s2

b. 2.205 N

Explanation:

We convert from rpm to rad/s knowing that each revolution has 2π radians and each minute is 60 seconds

200 rpm = 200 * 2π / 60 = 21 rad/s

180 rpm = 180 * 2π / 60 = 18.85 rad/s

r = d/2 = 30cm / 2 = 15 cm = 0.15 m

a)So if the angular speed decreases steadily (at a constant rate) from 21 rad/s to 18.85 rad/s within 10s then the angular acceleration is

\alpha = \frac{\Delta \omega}{\Delta t} = \frac{21 - 18.85}{10} = 0.21 rad/s^2

b) Assume the grind stone is a solid disk, its moment of inertia is

I = mR^2/2

Where m = 28 kg is the disk mass and R = 0.15 m is the radius of the disk.

I = 28*0.15^2/2 = 0.315 kgm^2

So the friction torque is

T_f = I\alpha = 0.315*0.21 = 0.06615 Nm

The friction force is

F_f = T_f/R = 0.06615 / 0.15 = 0.441 N

Since the friction coefficient is 0.2, we can calculate the normal force that is used to press the knife against the stone

N = F_f/\mu = 0.441/0.2 = 2.205 N

7 0
3 years ago
The conductor is initially electrically neutral, and then a charge q is placed at the center of the hollow space. Suppose the co
Anvisha [2.4K]

The total charge on the interior of the conductor is zero.

The total charge on the exterior of the conductor is 8q.

<h3>Total charge on the interior</h3>

Due to large number of electrons available for conduction in a conductor, most of the electrons moves to surface leaving zero net charge inside the conductor.

Thus, the total charge on the interior of the conductor is zero.

<h3>Total charge on the exterior</h3>

The total charge on the exterior of the conductor is calculated as follows;

Q = q + 7q = 8q

Thus, the total charge on the exterior of the conductor is 8q.

Learn more about net charge on interior and exterior of conductors here: brainly.com/question/14653264

7 0
2 years ago
What dictates the minimum and maximum pressure allowed for plumbing fixtures?
DENIUS [597]
The answer is: the building codes, which are a set of rules that regulate the conditions that a building must meet. Those requirements are very important to guarantee safety of both the people who are building it and the people who are going to work or live inside of the building in the future
8 0
3 years ago
Read 2 more answers
To calculate the change in kinetic energy, you must know the force as a function of _______. The work done by the force causes t
QveST [7]

Answer:

(c) position

Explanation:

From the work-energy theorem, the workdone by a force on a body causes a change in kinetic energy of the body.

But, remember that the work done (W) by a force (F) on a body is the product of the force and the distance d, moved by the body caused by the force. i.e

W = F x d

This distance is a measure of the position of the body at a given instance.

Therefore, the work done is given by the force as a function of distance (or position).

3 0
3 years ago
Identical isolated conducting spheres 1 and 2 have equal charges and are separated by a distance that is large compared with the
scoundrel [369]

Answer:

F = 0.1575 N

Explanation:

When the third sphere touches the first sphere, the charge is distributed between both spheres, then now the first sphere has only half of his original charge.

In this moment then

Sphere one has a charge = Q/2

Sphere three has a charge = Q/2

Now when the third sphere touches the second sphere again the charge is distributed in a manner that both sphere has the same charge.

How the total charge is Q = Q/2 + Q = 3/2Q, when the spheres are separated each one has 3/4Q

Sphere two has a charge = 3/4Q

Sphere three has a charge = 3/4Q

The electrostatic force that acts on sphere 2 due to sphere 1 is:

F = \frac{kQ_{1}Q_{2} }{r^{2} }

F= \frac{K(Q/2)(3Q/4)}{r^{2} }

how \frac{KQ^{2} }{r^{2} } = 0.42

Then

F = \frac{0.42*3}{8}

F = 0.1575 N

3 0
3 years ago
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