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3 years ago

Is the reduction of copper from copper(ii) oxide by carbon exothermic or endothermic? what is the sign of the energy change?

Physics

1 answer:

Sloan [31]3 years ago

8 0

Answer;

-Exothermic reaction;

-The sign of the energy change is negative (-)

Explanation;

2CuO(s) + C(s) --> 2Cu(s) + CO2(g)

ΔH = ΣΔHf(products) - ΣΔHf(reactants)

ΔH = -393.5kJ - 2(-155.2kJ) = -83.1 kJ

The reaction is exothermic.

-An exothermic process or reaction releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings.

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The froghopper, Philaenus spumarius, holds the world record for insect jumps. When leaping at an angle of 58.0 above the horizon

kirza4 [7]

Answer:

A) 3.79 m/s B) 1.33 m

Explanation:

Horizontal movement:
Once in the air, no forces act on the froghopper, so it keeps moving with the same initial horizontal speed.
This horizontal component, is the projection of the velocity vector on the horizontal direction (x-axis):

$v_{ox} = v_{o} *cos (58.0 deg)$

The horizontal displacement can be simply calculated as follows:

$x = v_{ox} *t$

Vertical movement:
As the vertical and horizontal are independent each other (due to they are perpendicular, so there is no projection of one movement on the other), in the vertical direction, all happens as if would be a body thrown upward with a given initial vertical velocity.
This velocity can be found as the projection of the velocity vector on the vertical direction (y-axis):

$v_{oy} = v_{o} *sin (58.0 deg) (1)$

Once in the air, the gravity will cause that the froghopper be slow down, till it reaches to the maximum height, where it will come momentarily to an stop.
In that moment, we can apply the following kinematic equation:

$v_{fy} ^{2} -v_{oy} ^{2} = 2*g*h_{max}$

where vfy = 0, g = -9.8m/s2, hmax = 52.7 cm= 0.527 m
Replacing by the givens, we can solve for voy:

$v_{oy} =\sqrt{2*g*h_{max}} = \sqrt{2*9.8m/s2*0.527m} =3.21 m/s$

From the equation (1), we can solve for the magnitude of the initial velocity, v₀:

$v_{o} = \frac{v_{oy}}{sin 58.0} =\frac{3.21m/s}{0.848} = 3.79 m/s$

With the value of the magnitude of the initial velocity, we can find the horizontal component vox, as follows:

$v_{ox} = v_{o} *cos (58.0 deg) =\\ \\ 3.79 m/s * cos (58.0deg) = 2.01 m/s$

In order to know the horizontal distance travelled, we need to find the time that the insect was in the air.
We can use the equation for the vertical displacement, replacing this value by 0, as follows:

$y = 0 = v_{oy} *t -\frac{1}{2} * g *t^{2}$

Replacing by the givens, and rearranging terms, we can solve for t:

$t_{air} =\frac{2*v_{oy} }{g} = \frac{2*3.21 m/s}{9.8 m/s} = 0.66 s$

Finally, we find the horizontal displacement, as follows:

$x_{max} = v_{ox} *t_{air} = 2.01 m/s * 0.66 s \\ \\ x_{max} = 1.33 m$

The horizontal distance covered by the froghopper was 1.33 m.

4 0

3 years ago

The flywheel in the shape of a solid cylinder of mass 75.0 kg and diameter 1.40 m rotates about an axis passing through the cent

Anni [7]

The torque required for the cylinder is 76.99 N m.

What is torque?

Torque may be defined as the product of the force and the distance perpendicular to the force from the axis of rotation.

Calculation of the angular acceleration:

The first kinematic equation for the rotational motion is,

ω=ω₀+αt

where ω₀ is the initial angular velocity, ω is the final angular velocity, α is the angular acceleration and t is the time. Since the cylinder starts from the rest, its initial angular velocity is zero.

Here, ω=320 rev/min or ω=320*2π/60 rad/sec, ω₀=0 and t=8.00 sec. Put these values in the above equation and solve it to get the value of angular acceleration.

320*2π/60=0+α*8

α=320*2π/(8*60)

α=4.19 rad/s^2

Calculation of the torque:

The torque T is given by the formula,

T=Iα

where I is the moment of inertia.

For the cylinder, I=1/2*mr^2

where m is the mass of the cylinder and r is the radius of the cylinder.

So,

T=1/2*mr^2*α

Here m=75 kg, radius r is half of the diameter r=1.4/2=0.7 m, and α=4.19 rad/s^2. Using these values in the formula of torque.

T=1/2*(75)*(0.7)^2*4.19

T= 76.99 N m

Learn more about the torque.

brainly.com/question/16049994

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6 0

2 years ago

2 Jupiter orbits the sun in a nearly circular path with radius 7.8x10^11m. The orbital period of Jupiter is 12 years.

bazaltina [42]

Mass of Jupiter=1.9×10

㎏=M

Mass of Sun=1.99×10

㎏=M

Mean distance of Jupiter from Sun=7.8×10

m=r

G=6.67×10

−11

N㎡㎏

−2

Gravitational Force, F=

(7.8×10

)

6.67×10

−11

×1.9×10

×1.99×10

F=4.16×10

4 0

2 years ago

The direction of current in a solenoid depends on the direction of magnetic field’. Do you agree with this statement? Showthe pa

iogann1982 [59]

Answer:

1) Yes the direction of the magnetic field is found based on Fleming's Right Hand Rule

2) The pattern indicates the direction of the magnetic force field lines

Explanation:

1) The solenoid is the is the coil of electric conductor that when it carries an electric current produces a magnetic field

According to Fleming's Right Hand Rule, the direction of the magnetic field produced by a solenoid, depends on the direction of the current such that when the direction of the conventional current is in the direction of the wrapped fingers, the thumb points in the direction of the magnetic field which is North N.

2) The pattern of field lines inside the solenoid indicates the direction of the generated magnetic field moving from left to right within the solenoid as the electric current moves around in the direction shown in the diagram.

7 0

3 years ago

A massless rod of length L has a small mass m fastened at its center and another mass m fastened at one end. On the opposite end

konstantin123 [22]

Answer:

onservation of energy

U top = K bottom

(m + m)*g*L = 1/2*I*?^2 where I = m*(L/2)^2 + m*L^2 = 1.25*m*L^2

So 2m*g*L = 1/2*1.25*m*L^2*?^2

So ? = sqrt(3*g*/(1.25*L) ) = sqrt(12g/5L)

3 0

3 years ago