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3 years ago

HELP ASAP!!! What was Johann Dobereiner’s contribution to the development of the periodic table?

Physics

2 answers:

Nataly_w [17]3 years ago

8 0

He identified triads of elements that had similar properties

galina1969 [7]3 years ago

6 0

Answer;

3) He identified triads of elements that had similar properties.

Explanation;

Each of Dobereiner's triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other.

Dobereiner discovered that the relative atomic mass of the middle element in each triad was close to the average of the relative atomic masses of the other two elements. This gave other scientists a clue that relative atomic masses were important when arranging the elements.

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You are designing a delivery ramp for crates containing exercise equipment. The 1470-N crates will move at 1.8 m/s at the top of

alina1380 [7]

Answer:

The force constant ,I = 2394N/m

Explanation:

Given:

Weight of crate,Wg = 1470N

Theta = 22.0°

Kinetic friction,Fk= Fs(max) = 550N

Total length of ramp =8.0m

If y =0 at the bottom of the ramp

y1 = d Sin theta

y1 = 8 × Sin 22°

y1 = 3.0m

y2 = 0

V1=1.8m/s

V2 = 0

The equation combining the gravitational and elastic potential energy, and the work energy theorem is given by:

K1 + Ugrav1 + Uel1 + W = K2 + Uel1 ..eq1

Where KE is given by: 1/2mv^2

Gravitational potential energy is given by: Ugrav = mgy ...eq2

Elastic potential energy = Uel = 1/2Kx^2 ..eq3

The restoring force constant of a spring compressed by a distance x is given by:

Fx = Kx ..eq4

Workdone by a constant force is given by W = Fscostheta ...eq5

Where s = displacement

Theta = the angle between the force and the displacement

Work,W = Wf = 550 ×8 × cos 180°

W = -4400J

From the weight of the crate.mass is:

Wg/g = m

1470/9.8 = 150kg

K1 = 1/2 ×150×1.8^2 = 243m/s

The crate comes to rest at K2=0

Ugrav1 = 150 × 9.8 × 3 = 4410J

Ugrav2 = 150 × 9.8 x 0 = 0J

Uel1= 0 Spring at equilibrium

Substituting the values of the energies and work

253 + 4410 + 0 - 4400 = 0 + 0 + Uel1

Uel1 = 253J

Substituting into eq3

253 = 1/2 Kx^2 = 1/2 Kx(x)

Kx = 506/x

Since crate remains at rest,we use Newton's 2nd law

Fx = fs + Wsin theta

Fx = 550 + 1470 sin 22

Fx = 1100.7N

Substituting into eq4

Kx = 1100.7

X = 506/1100.7 = 0.46m

Kx = 1100.7

K = 1100.7/0.47

K = 2394N/m

5 0

3 years ago

What is the weight of a person who has a mass of 76 kg?

liq [111]

Answer:

<h2>744.8N is the answer . Explanation is in the attachment .</h2>

5 0

3 years ago

a u tube contains a liquid of an unknown density an oil of density is poured into the right arm of the tube until the oil column

scoray [572]

Answer:

The answer is " $1155\ \frac{kg}{m^3}$ "

Explanation:

Please find the complete question in the attached file.

$p = p_0 + ?gh$

pi = pressure only at two liquids' devices

PA = pressure atmosphere.

1 = oil density

2 = uncertain fluid density

$h_1 = 11 \ cm\\\\h_2= 3 \ cm$

The pressures would be proportional to the quantity $11-3 = 8$ cm from below the surface at the interface between both the oil and the liquid.

$\to p_A + ?2g(h_1 - h_2) = p_A + ? 1gh_1\\\\\to ?2 = \frac{?1h_1}{(h_1 - h_2)} \\\\$

$= \frac{840 \frac{kg}{m^3}}{\frac{11}{8}} \\\\= 1155\ \frac{kg}{m^3}$

8 0

3 years ago

The input work done on a machine is 9.63 × 103 joules, and the output work is 3.0 × 103 joules. What is the percentage efficienc

notsponge [240]

Input work = 9.63×10³ J.
Output work = 3.0×10³ J

By definition,
Efficiency = (Output work)/(Input work)
= (3.0×10³)/(9.63×10³)
= 0.31 = 31%

Answer: 31%

5 0

3 years ago

Read 2 more answers

A springboard diver intending to do a somersault brings her knees and arms closer to her body during the dive. What effect does

Hoochie [10]

During the diving when a diver jumps off from platform he brings her knees and arms closer to the body

This is because when diver is in air he don't have any torque about his center of mass which shows that angular momentum of his body will remain constant during his motion in air

Now we can say product of his moment of inertia and his angular speed will remain constant always

So here if we decrease the moment of inertia of the body during our motion then angular speed will increase so that product will remain constant

and this is what the diver use during his diving

so correct answer will be

It decreases her moment of inertia.

7 0

3 years ago