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3 years ago

Testing shows that a sample of wood from an artifact contains 25% of the

Physics

2 answers:

daser333 [38]3 years ago

5 0

Answer:

The artifact is 11,460 years old.

Explanation:

Given that,

The half life of the carbon-14 is 5730 years and we are left with 255 of the sample of wood from an arti-fact.

So it takes 5730 years for the sample to reduce into half

Initially there will be 100% of the sample so

after first 5730 years, the sample reduces into 50% percent

Now the left 50% sample will take another 5730 years to decay into half of its amount.

after next 5730 years the sample reduces into 25% percent

So totally after 2 half-life the sample reduces into 25%

That is (5730 +5730) years = 11460 years

Umnica [9.8K]3 years ago

3 0

Answer:5730 years

Explanation:

A P E X

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A total of 25.6 kJ of heat energy is added to a 5.46 L sample of helium at 0.991 atm. The gas is allowed to expand against a fix

bagirrra123 [75]

Answer:

(a) W = 1329.5 J = 1.33 KJ

(b) ΔU = 24.27 KJ

Explanation:

(a)

Work done by the gas can be found by the following formula:

$W = P\Delta V$

where,

W = Work = ?

P = constant pressure = (0.991 atm)( $\frac{101325\ Pa}{1\ atm}$ ) = 100413 Pa

ΔV = Change in Volume = 18.7 L - 5.46 L = (13.24 L)( $\frac{0.001\ m^3}{1\ L}$ ) = 0.01324 m³

Therefore,

W = (100413 Pa)(0.01324 m³)

W = 1329.5 J = 1.33 KJ

(b)

Using the first law of thermodynamics:

ΔU = ΔQ - W (negative W for the work done by the system)

where,

ΔU = change in internal energy of the gas = ?

ΔQ = heat added to the system = 25.6 KJ

Therefore,

ΔU = 25.6 KJ - 1.33 KJ

ΔU = 24.27 KJ

3 0

3 years ago

How significant is air resistance for projectile motion?

miv72 [106K]

Answer:

Air resistance have some significant role in projectile motion if the motion lasts for some time.

Explanation:

Air resistance or air drag seems to be important in daily actvities and games like baseball.

The trajectory of the projectile with or without air resistance or air drag is totally different.

When we neglect air drag, the only acting force is gravity against the motion so the maximum height and range are suppose Hmax and R.

Now, when we consider air drag, it is important to notice that there are two forces against the motion of the ball and along the direction of gravity. It seems that both maximum height and range are lesser Hmax'< Hmax and R'<R.

8 0

2 years ago

You, Archimedes, suspect that the king’s crown is not solid gold but is instead gold-plated lead. To test your theory, you weigh

hjlf

Answer:

a) 16675.75 Kg/m³ b) 77.6%

Explanation:

the weight of the crown = 60 N, density of gold = 19300 Kg/m^3, density of lead = 11340 kg/m^3, density of water = 1000kg/m^3 and acceleration due to gravity = 9.8 m/s^2

upthrust on the crown = weight in air - weight when fully submerged in water = 60 - 56.4 = 3.6 N

mass of water displaced = 3.6 / 9.8 since weight = mass × g

mass of water displaced = 0.367 Kg

density of water = mass / volume

1000 = 0.367 / volume

cross multiply and find volume

volume of the crown = 0.367 / 1000 = 0.000367 m³ since the crown will displace water of equal volume according to Archimedes principle

Let V1 represent the volume of Gold and let V2 represent the volume of lead

Total volume of the crown = V1 + V2

also

density of gold = mass of gold / V1 and density of lead = mass of lead / V2

19300 = mass of gold in the crown / V1 and 11340 = mass of lead in the crown / V2

19300 V1 = mass of gold and 11340 V2 = mass of lead

add the two together

19300 V1 + 11340 V2 = weigth of the crown / 9.8

19300 V1 + 11340 V2 = 6.12 also

V1 + V2 = 0.000367

make V1 subject of the formula in equation 2

V1 = 0.000367 - V2

substitute for V1 in equation 1

19300 (0.000367 - V2) + 11340 V2 = 6.12

open the bracket

7.083 - 19300 V2 + 11340 V2 = 6.12

rearrange the equation

-7960 V2 = 6.12 - 7.083

-7960 V2 = -0.963

V2 = -0.963 / -7960 = 0.000121 (volume of lead in the crown)

substitute V2 into equation 2

V1 + 0.000121 = 0.000367m³

V1 = 0.000367 - 0.000121 = 0.000246m³ (volume of gold in the crown)

so mass of gold in the crown = 19300 × 0.000246 = 4.748 kg

and mass of lead = 11340 × 0.000121 = 1.372 kg

average density of the crown = (mass of gold + mass of lead) / total volume = 6.12 / 0.000367 = 16675.75 kg/ m³

b) percentage make of gold = mass of gold / total mass × 100 = 77.6 % approx

4 0

2 years ago

An object has a mass of 10.2 kg, what is its weight in Newton's?

Juliette [100K]

Answer:

The answer is 98 N

Explanation:

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3 0

2 years ago

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A spring is characterized by a spring constant of 60 N/m. How much potential energy does it store, when stretched by 1.0 cm?

Anestetic [448]

Answer:

3.0 x10^-3 J

Explanation:

The potential energy of a spring is given by PE = (0.5)k*x^2

Where

K: Spring Constant = 60 N/m

x: displacement of the spring from its equilibrium position = 1cm = 0.01m

Then PE = 0.5(60)(.01)^2 = 0.003J = 3.0 x10^-3 J

8 0

3 years ago

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