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2 years ago

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An unknown substance weighing 0.545g is placed into a bomb calorimeter with a heat capacity of 6.75 kJ/°C. When the sample is bu

rned completely, the temperature in the calorimeter rises from 23.3°C to 26.4°C.

1 answer:

Leokris [45]2 years ago

7 0

Answer:

heat generated by the reaction = 20.925 kJ

Explanation:

Assuming that the we asked heat generated by the reaction.

$Q=C(T_2-T_1)$

C= heat capacity = 6.75 KJ/°C

C= Cp×m

T_2= 26.4°C and T_1= 23.3°C

$Q=6.75\times(26.4-23.3)$

=20.925 kJ

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One end of a piano wire is wrapped around a cylindrical tuning peg and the other end is fixed in place. The tuning peg is turned

liq [111]

Answer:

$T = 3183 N$

Explanation:

When the screw is turned by two turns then change in the length of the wire is given as

$\Delta L = 2(2\pi r)$

$\Delta L = 4\pi r$

$\Delta L = 4(\pi)(1.0 mm)$

$\Delta L = 12.56 mm$

now we know by the formula of Young's modulus

$Y = \frac{T/A}{\Delta L/L}$

so we have

$T = \frac{AY \Delta L}{L}$

$T = \frac{\pi (0.55 \times 10^{-3})^2(2.0 \times 10^{11})(12.56 \times 10^{-3})}{0.75}$

$T = 3183 N$

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2 years ago

An archer draws her bow and stores 34.8 J of elastic potential energy in the bow. She releases the 63 g arrow, giving it an init

elena-14-01-66 [18.8K]

Answer:

Approximately $71\%$ .

Explanation:

The formula for the kinetic energy $\rm KE$ of an object is:

$\displaystyle \mathrm{KE} = \frac{1}{2}\, m \cdot v^2$ ,

where

$m$ is the mass of that object, and
$v$ is the speed of that object.

Important: Joule ( $\rm J$ ) is the standard unit for energy. The formula for $\rm KE$ requires two inputs: mass and speed. The standard unit of mass is $\rm kg$ while the standard unit for speed is $\rm m \cdot s^{-1}$ . If both inputs are in standard units, then the output (kinetic energy) will also be in the standard unit (that is: joules,

Convert the unit of the arrow's mass to standard unit:

$m = 63\; \rm g = 0.063\; \rm kg$ .

Initial $\rm KE$ of this arrow:

$\begin{aligned}\mathrm{KE} &= \frac{1}{2} \, m \cdot v^2 \\ &= \frac{1}{2}\times 0.063\; \rm kg \times \left(\rm 28 \; m \cdot s^{-1}\right)^2 \\ &\approx 24.696\; \rm J\end{aligned}$ .

That's the same as the energy output of this bow. Hence, the efficiency of energy transfer will be:

$\displaystyle \frac{24.696\; \rm J}{34.8\; \rm J} \times 100\% \approx 71\%$ .

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2 years ago

The magnetic field around the head has been measured to be approximately 3.00×10−8 gauss . Although the currents that cause this

konstantin123 [22]

Answer:

$3.81972\times 10^{-7}\ A$

Explanation:

B = Magnetic field = $3\times 10^{-8}\ G$

d = Diameter of loop = 16 cm

r = Radius = $\frac{d}{2}=\frac{16}{2}=8\ cm$

i = Current

$\mu_0$ = Vacuum permeability = $4\pi \times 10^{-7}\ H/m$

The magnetic field of a loop is given by

$B=\frac{\mu_0i}{2r}\\\Rightarrow i=\frac{B2r}{\mu_0}\\\Rightarrow i=\frac{3\times 10^{-8}\times 10^{-4}\times 2\times 0.08}{4\pi\times 10^{-7}}\\\Rightarrow i=3.81972\times 10^{-7}\ A$

The current needed to produce such a field at the center of the loop is $3.81972\times 10^{-7}\ A$

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2 years ago

A jogger accelerates from rest to 3.0 m/s in 2.0 s. A car accelerates from 38.0 to 41.0 m/s also in 2.0 s. (a) Find the accelera

Tom [10]

Answer:

a) The acceleration of the jogger is 1.5 m/s²

b) the acceleration of the car is also 1.5 m/s²

c) Yes, the car travels 76 m farther than the jogger.

Explanation:

a) The acceleration of an object is the variation of its velocity over time:

a = final velocity - initial velocity / time

for the jogger:

a = 3.0 m/s - 0 m/s / 2.0 s = <u>1.5 m/s ²</u>

b) For the car:

a = 41.0 m/s - 38.0 m/s / 2.0 s = <u>1.5 m/s²</u>

c) Let´s see the position of the car after 2 seconds.

The equation for the position of an accelerated object moving in a straight line is:

x = x0 + v0* t +1/2 * a * t²

Where:

x = position of the car at time "t"

x0 = initial position

v0 = initial velocity

t = time

a = acceleration

Let´s consider x0 = 0 because the origin of the reference system is located where the car starts accelerating. Then:

x = 38,0 m/s * 2 s + 1/2 * 1.5 m/s ² * (2.0 s)²

x = 79 m

In the same way, we can calculate the position of the jogger:

x = 0 m/s * t + 1/2 * 1.5 m/s ² * (2.0 s)²

x = 3 m

<u>The car travels 79 m - 3 m = 76 m farther than the jogger</u>

4 0

2 years ago

An inclined plane is made out of a short plank of wood. It is used to move a 300N box up onto a tabletop 1m above the floor. Wha

Ronch [10]

Answer:

<em>The purpose of an inclinded plane is to make easier to move objects to a certain height.</em>

The technology behind this is about the Work you need to use to move the object upwards. Basically, when we use an inclined plane, we are splitting the net force, making easier to move. All this means, the force needed to move the objecto up will be lower, due to the inclined plane.

So, if the force needed is lower, then the work is also lower, because the work done is defined as the product between the force applied and the distance traveled.

<em>In addition, if we have a longer inclined plane, that means the force needed is even lower,</em> beacuse the distance is increased, but the Work is the same, because it only depends on the initial and final point.

Therefore, in this case, the work would remain the same and the mechanical advantage would increase. As we said before, the work needed will be the same despite the force decreases, because the distance increases, remaining the work as a constant. And the mechanical advantage increases, because it's easier to move if the inclined plane is longer.

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2 years ago

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