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3 years ago

a book is sitting still on your desk. are the forces acting on the book balanced or unbalanced? explain.

2 answers:

8 0

<span>They are balanced. If the forces were not balanced the book would move*. In this example, the downward force of gravity on the book is counterbalanced by the upthrust of the desk. </span>

fgiga [73]3 years ago

4 0

The answer to this is balanced. Remember the downward force of gravity on the book is counterbalanced by the upthrust of the desk. Note that moving objects can also have balanced forces acting on them. if an object is moving at a constant speed, the force acting on it are balanced. It they are unbalanced the object would either accelerate or decelerate.

Hope this helped. <span />

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A circular loop of wire with a radius of 12.0 cm and oriented in the horizontal xy-plane is located in a region of uniform magne

Ulleksa [173]

(a) 34 V

The average emf induced in the loop is given by Faraday-Newmann-Lenz law:

$\epsilon = -\frac{\Delta \Phi_B}{\Delta t}$ (1)

where

$\Delta \Phi_B$ is the variation of magnetic flux through the coil

$\Delta t = 2.0 ms = 0.002 s$ is the time interval

We need to find the magnetic flux before and after. The magnetic flux is given by:

$\Phi_B = BA$

where

B is the magnetic field intensity

A is the area of the coil

The radius of the coil is r = 12.0 cm = 0.12 m, so its area is

$A=\pi r^2 = \pi (0.12 m)^2 = 0.045 m^2$

At the beginning, the magnetic field is

$B_i = 1.5 T$

so the flux is

$\Phi_i = B_i A = (1.5 T)(0.045 m^2)=0.068 Wb$

while after the removal of the coil, the magnetic field is zero, so the flux is also zero:

$\Phi_f = 0$

so the variation of magnetic flux is

$\Delta \Phi = 0-0.068 Wb=-0.068 Wb$

And substituting into (1) we find the average emf in the coil

$\epsilon=-\frac{-0.068 Wb}{0.002 s}=34 V$

(b) Counterclockwise

In order to understand the direction of the induced current, we have to keep in mind the negative sign in Lenz's law (1), which tells that the direction of the induced current must be such that the magnetic field produced by this current opposes the variation of magnetic flux in the coil.

In this situation, the magnetic flux through the coil is decreasing, since the coil is removed from the field. So, the induced current must be such that it produces a magnetic field whose direction is the same as the direction of the external magnetic field, which is upward along the positive z-direction.

Looking down from above and using the right-hand rule on the loop (thumb: direction of the current, other fingers wrapped: direction of magnetic field), we see that in order to produce at the center of the coil a magnetic field which is along positive z-direction, the induced current must be counterclockwise.

4 0

3 years ago

Two point charges, q1 and q2, are separated by a distance r. if the magnitudes of both charges are doubled and their separation

Svet_ta [14]

It will stay the same. Electric force decreases with distance but increases with magnitude of charge. By doubling them both, they essentially cancel out and nothing changes

5 0

3 years ago

Read 2 more answers

A 0.76-kg block is hung from and stretches a spring that is attached to the ceiling. A second block is attached to the first one

sergey [27]

Answer:

1.54 kg

Explanation:

mass of first block (m) = 0.76 kg

acceleration due to gravity (g) = 9.8 m/s

what is the mass (m) of the second block

force = kx ⇒ mg = kx

mg = kx

where m is the mass, g is the acceleration due to gravity, k is the

spring constant and x is the extension

0.76 x 9.8 = kx

7.5 = kx

k = 7.5/x ... equation 1

when a second block is attached to the first one the amount of stretch triples (this means that extension (x) = 3x)

therefore the new mass becomes m + 0.76 and the extension

becomes 3x

with the new mass and extension, mg = kx now becomes

(m+0.76)g = k(3x) ... equation 2

Recall that k = 7.5/x from equation 1, substituting this value of k into

equation 2 we have

(m+0.76)g = $\frac{7.5}{x}$ × (3x)

(m+0.76)g = 7.5 × 3

substituting the value of g = 9.8 m/s^{2}

(m + 0.76) x 9.8 = 7.5 x 3

m + 0.76 = 22.5 ÷ 9.8

m + 0.76 = 2.3

m = 2.3 - 0.76 = 1.54 kg

4 0

4 years ago

Which computational model can be applied to the total internal energy of a system with two point masses?

I am Lyosha [343]

Answer:

Explanation:

Took the test :)

4 0

3 years ago

A machine part has the shape of a solid uniform sphere of mass 220 g and diameter 4.50 cm . It is spinning about a frictionless

miss Akunina [59]

Answer:

The angular acceleration is 10.10 rad/s².

Explanation:

Given that,

Mass of sphere =220 g

Diameter = 4.50 cm

Friction force = 0.0200 N

Suppose we need to find its angular acceleration.

We need to calculate the angular acceleration

Using formula of torque

$\tau=f\times r$

$I\times\alpha=f\times r$

Here, I = moment of inertia of sphere

$\dfrac{2}{5}mr^2\times\alpha=f\times r$

$\alpha=\dfrac{5\times f}{2mr}$

Put the value into the formula

$\alpha=\dfrac{5\times0.0200}{2\times220\times10^{-3}\times2.25\times10^{-2}}$

$\alpha=10.10\ rad/s^2$

Hence, The angular acceleration is 10.10 rad/s².

7 0

3 years ago