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3 years ago

What is the mass number of the isotope lithium-7??

Physics

2 answers:

svp [43]3 years ago

8 0

Explanation:

Mass number is the sum of total number of protons and total number of neutrons present in an atom.

For example, a neutral atom of lithium has mass number 7 and atomic number 3.

Atomic number means the total number of protons present in an atom.

So, isotope of lithium-7 will have 3 protons and 4 neutrons. Thus, mass number of lithium-7 will be 3 + 4 = 7.

FromTheMoon [43]3 years ago

5 0

Lithium-7 is by far the most-common isotope, making up about 92.5 percent of all natural lithium. A lithium-7 atom contains three protons, four neutrons, and three electrons.

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Two rocks are at the top of a building. Rock 1 is dropped from rest while Rock 2 is thrown horizontaly at a velocity of 5 ms.

LuckyWell [14K]

Answer:

I'm pretty sure the answer is 0 m/s²

Explanation:

The horizontal velocity of the second rock is 5 m/s, so if we pretend air resistance doesn't exist, it will maintain that horizontal velocity, meaning that there is no horizontal acceleration.

7 0

3 years ago

In an experiment, the 1 kg cart collides with a 3 kg cart but doesn’t stick to it. Instead, the 3 kg cart gets knock forward by

notka56 [123]

Explanation:

Given that,

Mass of the cart, $m_1=1\ kg$

Mass of the cart 2, $m_2=3\ kg$

Final speed of cart 2, $v_2=0.3\ m/s$

Final speed of cart 1 is 0 as it comes to rest.

Let us assume that the initial velocity of the cart 2 is 0. So using the conservation of linear momentum as :

$m_1u_1+m_2u_2=m_1v_1+m_2v_2\\\\m_1u_1+0=0+m_2v_2\\\\m_1u_1=m_2v_2\\\\u_1=\dfrac{m_2v_2}{m_1}\\\\u_1=\dfrac{3\times 0.3}{1}\\\\u_1=0.9\ m/s$

So, the initial velocity of the 1.0-kg cart is 0.9 m/s.

8 0

3 years ago

3). Classify the following as scalar and vector quantities.

Firdavs [7]

Answer:

option A C E F are scalar quantity option B D Are vector quantity

8 0

2 years ago

A conducting wire has a length of 3m and a resistance of 0.35 Ώ , when a potential difference is applied to the ends of the wire

NikAS [45]

Answer: E = IR/L

E= 1.8A*0.35Ω/3m=0.21

Explanation:

7 0

3 years ago

2. Cell phones work by receiving and emitting radiation in the range of 1.9-2.2 Giga Hertz (GHz). This is about 1.9 X 109 -2.2 X

serious [3.7K]

A) 0.136 - 0.158 m

B) Microwaves

Explanation:

For an ectromagnetic wave, there is a relationship between its frequency and its wavelength, contained in the wave equation:

$\lambda=\frac{c}{f}$

where

$\lambda$ is the wavelength of the wave

$c=3.0\cdot 10^8 m/s$ is the speed of light in a vacuum

f is the frequency of the wave

For the waves in this problem, we have:

$f_1=1.9\cdot 10^9 Hz$ is the minimum frequency

$f_2=2.2\cdot 10^9 Hz$ is the maximum frequency

Therefore, the range of corresponding wavelengths is:

$\lambda_1=\frac{3\cdot 10^8}{1.9\cdot 10^9}=0.158 m$

$\lambda_2=\frac{3\cdot 10^8}{2.2\cdot 10^9}=0.136 m$

Electromagnetic waves are oscillations of the electric and the magnetic field occurring in a plane perpendicular to the direction of motion the wave.

All electromagnetic waves travel in a vacuum always at the same speed, the speed of light ( $c=3.0\cdot 10^8 m/s$ ).

Electromagnetic waves are classified into 7 different types, according to their wavelength and frequency. From the longest to the shortest wavelength, we have:

Radio waves (>1 m)

Microwaves (1 mm - 1 m)

Infrared (750 nm - 1 mm)

Visible light (380 nm - 750 nm)

Ultraviolet (10 nm - 380 nm)

X-rays (0.01 nm - 10 nm)

Gamma rays (<0.01 nm)

Therefore, we see that the waves in this problem (of wavelength between 0.136 and 0.158 m) are classified as microwaves.

8 0

3 years ago