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3 years ago

13

Suppose heat has caused convection currents to from in a fluid. When the heat source is removed from the fluid, the convection c

urrents will A. speed up B. change direction C. eventually stop D. continue at the same rate forever

1 answer:

RideAnS [48]3 years ago

7 0

The answer to the question is (C)
Hope this helps :)

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A 50 g sample of an unknown metal is heated to 90.0C. It is placed in a perfectly insulated container along with 100 g of water

Scrat [10]

Answer:

0.64 J/g°C

Explanation:

Using the formula;

Q = m × c × ∆T

Where;

Q = amount of heat

m = mass (g)

c = specific heat capacity

∆T = change in temperature (°C)

In this case:

Q (water) = - Q (metal)

mc∆T (water) = - mc∆T (metal)

According to the information in this question,

For water; m = 100g, c = 4.18J/g°C, ∆T = (25°C - 20°C)

For metal; m = 50g, c =?, ∆T = (25°C - 90°C)

mc∆T (water) = - mc∆T (metal)

100 × 4.18 × (25°C - 20°C) = - {50 × c × (25°C - 90°C)}

100 × 4.18 × 5 = - {50 × c × -65}

2090 = -{-3250c}

2090 = 3250c

c = 2090/3250

c = 0.643

c = 0.64J/g°C

7 0

3 years ago

Read 2 more answers

You want to use the idea of electromagnetic induction to make the bulb in your small flashlight glow; it glows when the potentia

makkiz [27]

a) 57.5 m/s

b) Yes

Explanation:

a)

According to Faraday-Newmann-Lenz's law, the electromotive force induced in the coil due to the change in magnetic flux through it is given by:

$\epsilon=-\frac{N \Delta \Phi}{\Delta t}$

where

N is the number of turns in the coil

$\Delta \Phi$ is the change in magnetic flux

$\Delta t$ is the time interval

The change in magnetic flux can be written as

$\Delta \Phi = A\Delta B$

where

A is the area of the coil

$\Delta B$ is the variation of the strength of the magnetic field

Re-writing the equation,

$\epsilon=-\frac{NA\Delta B}{\Delta t}$

To make the bulb glowing, the induced emf must be:

$\epsilon=1.5 V$

And we also have:

N = 100

$\Delta B=0 T-3.6\cdot 10^{-2} T=-0.036 T$

$A=2.9\cdot 10^{-4} m^2$

So we can find the maximum time required to induce this emf:

$\Delta t=-\frac{NA\Delta B}{\epsilon}=-\frac{(100)(2.9\cdot 10^{-4})(-0.036)}{1.5}=6.96\cdot 10^{-4} s$

Since the length to cover in this time is

L = 4.0 cm = 0.04 m

The speed should be

$v=\frac{L}{t}=\frac{0.04}{6.96\cdot 10^{-4}}=57.5 m/s$

b)

Yes: if the coil is moved at a speed of 57.7 m/s, then the potential difference induced in the bulb will be 1.5 V, which is enough to make the bulb glowing.

6 0

3 years ago

What do astronomers mean when they say that we are all star stuff?.

tekilochka [14]

Answer:

low-mass star.

Explanation:

Pls, choose me as brainliest!

7 0

3 years ago

Read 2 more answers

A ball is spun around in circular motion such that it completes 50 rotations in 25 s. What is the frequency of its rotation? 2.

Elis [28]

Answer:

1. $f = 2 Hz$

2. $f = 0.011 Hz$

3. $f = 0.067 Hz$

4. $t = 4 s$

Explanation:

1. The frequency of rotation is given by:

$f = \frac{\omega}{2\pi}$

Where:

ω: is the angular speed = 50 rotations (revolutions) in 25 s.

We need to convert the units of ω.

$\omega = \frac{50 rev}{25 s}*\frac{2\pi rad}{1 rev} = 4\pi rad/s$

Now, the frequency is:

$f = \frac{4\pi rad/s}{2\pi} = 2 Hz$

2. The frequency is:

We know:

5 laps = 5 revolutions

t: time = 450 s

$f = \frac{\omega}{2\pi} = \frac{\frac{5 rev}{450 s}*\frac{2\pi rad}{1 rev}}{2\pi} = 0.011 Hz$

3. The frequency of the pendulum is:

$f = \frac{\omega}{2\pi} = \frac{\frac{1 rev}{15 s}*\frac{2\pi rad}{1 rev}}{2\pi} = 0.067 Hz$

4. We have:

θ: number of revolutions = 48 rev

f = 12 Hz

t =?

The time can be calculated as follows:

$f = \frac{\omega}{2\pi} = \frac{\theta}{2\pi t}$

$t = \frac{\theta}{2\pi f} = \frac{48 rev*\frac{2\pi rad}{1 rev}}{2\pi*12 Hz} = 4 s$

I hope it helps you!

4 0

3 years ago

Energy transformed by a moving object is

QveST [7]

Kinetic energy is the energy an object has because of its motion. If we want to accelerate an object, then we must apply a force. ... Kinetic energy can be transferred between objects and transformed into other kinds of energy

4 0

4 years ago