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3 years ago

Someone help me please i need to finish this

Physics

2 answers:

Ilya [14]3 years ago

8 0

Answer:

D. A zinc Zn contains 30 protons inside the nucleus and 30 electron outside the nucleus

gavmur [86]3 years ago

5 0

Answer:

the last option is correct

Explanation:

see I won't explain all the points but will tell you the concept being used.

protons and neutrons are inside the nucleus in an atom while the electrons are outside the nucleus.

the mass number of an atom is equal to the sum of number of electrons and neutrons in an atom
atomic number is equal to the number of electrons which is equal to the number of protons in an atom
no. of electrons/ protons is always less than that of neutrons and they're almost equal( a large difference ain't obtained between the number of electrons and that of neutrons.

since, the rest of the options are violating the above rules they're incorrect

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If F1 = 390 N and F2 = 550 N , determine the angle θ(0∘≤θ≤180∘) between them, so that the resultant force has a magnitude of FR

Nadya [2.5K]

Answer:

Explanation:

R² = F₁² + F₂² + 2F₁F₂ Cosθ , R is resultant force , θ is angle between them

780² = 390² + 550² + 2 x 390 x 550 Cosθ

608400 = 152100 + 302500 + 429000 Cosθ

Cosθ = .3585

θ = 69 degree.

5 0

3 years ago

It takes a minimum distance of 41.14 m to stop a car moving at 11.0 m/s by applying the brakes (without locking the wheels). Ass

padilas [110]

Answer:

Find the time it took for the car to stop at 11.0m/s

V = deltax/t

t = 41.14/11.0 = 3.74s

Now find at what rate it was decelerating, so find the acceleration during that interval of time.

vf = vi + at

-11.0m/s = a3.74s

a = -2.94m/s^2

The acceleration is negative because is pulling the car towards its opposite direction to make it stop.

Now find how much time it would take for the car to stop at 28.0m/s but with the same acceleration, the car is the same so its acceleration to stop the car will remain the same.

vf = vi + at

0 = 28.0 - 2.94t

t = 9.52

Once the time is obtained, you can find the final position, xf, by plugging the time acceleration and velocity values.

xf = 0 + (28m/s)(9.52s) + 1/2(-2.94)(9.52s)^2

xf = 266.6m - 133.23m = 133m

8 0

4 years ago

After three half-lives, one-ninth of an original radioactive parent isotope remains, and eight-ninths has decayed into the daugh

BartSMP [9]

Answer:

B. False

The true statement will be:

After three half-lives, one-eighth of an original radioactive parent isotope remains, and seven-eighth has decayed into daughter isotopes.

Explanation:

Half life means the time after which the amount of the given substance becomes half of its initial amount, by radiation.

Thus after each successive half life the material is halved or half of it is decayed, which leads to a general formula:

Remaining Amount = 1/2^n of parent isotope

where, n is the number of half lives passed. So, for three half-lives:

Remaining Amount = 1/2^3 of parent isotope

Remaining Amount = 1/8 of parent isotope

Thus, the decayed amount will be:

Decayed Amount = (1-1/8) of parent isotope

Decayed Amount = 7/8 of parent isotope

Thus, the given statement is B.False

8 0

3 years ago

A man, facing a high wall, notices that an echo is heard 4.0 seconds after he makes a sharp sound. After walking 200m directly t

cestrela7 [59]

Answer:2.4

Explanation:basically 2.4 = 2.500 kg and then we add 3.4 seconds in all of them 4.0 + 3.4 = 2.5 ok

4 0

3 years ago

three masses are connected by a light string that passes over a frictionless pulley as shown. (a) what is there acceleration of

Ket [755]

The mass on the left has a downslope weight of

W1 = 3.5kg * 9.8m/s² * sin35º = 19.7 N

The mass on the right has a downslope weight of

W2 = 8kg * 9.8m/s² * sin35º = 45.0 N

The net is 25.3 N pulling downslope to the right.

(a) Therefore we need 25.3 N of friction force.

Ff = 25.3 N = µ(m1 + m2)gcosΘ = µ * 11.5kg * 9.8m/s² * cos35º

25.3N = µ * 92.3 N

µ = 0.274

(b) total mass is 11.5 kg, and the net force is 25.3 N, so

acceleration a = F / m = 25.3N / 11.5kg = 2.2 m/s²

tension T = 8kg * (9.8sin35 - 2.2)m/s² = 27 N

Check: T = 3.5kg * (9.8sin35 + 2.2)m/s² = 27 N √

hope this helps. :)

3 0

4 years ago