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3 years ago

Which of the following is a vector quantity?

2 answers:

6 0

Since vectors are essentially quantities that have direction, D must be the answer as it contains a direction (down) while the other ones do not.

otez555 [7]3 years ago

3 0

A vector is a quantity with a size and a direction.

The only choice that has both of those is D .

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An electron is projected with an initial speed vi = 4.60 × 105 m/s directly toward a very distant proton that is at rest. Becaus

frutty [35]

Answer:

$2.99\times 10^{-19}\ m$

Explanation:

Given:

$u$ = initial velocity of the electron = $4.60\times 10^5\ m/s$

$v$ = final velocity of the electron = $3u$

$x$ = initial position of the electron from the proton = very distant = $\infty$

Assume:

$m$ = mass of an electron = $9.1\times10^{-31}\ kg$

$e$ = magnitude of charge on an electron = $1.6\times10^{-19}\ C$

$p$ = magnitude of charge on an proton = $1.6\times10^{-19}\ C$

$k$ = Boltzmann constant = $9\times 10^9\ Nm^2/C^2$

$y$ = final position of the electron from the proton

$\Delta K$ = change in kinetic energy of the electron

$W$ = work done by the electrostatic force

$F$ = electrostatic force

$r$ = instantaneous distance of the electron from the proton

Let us first calculate the work done by the electrostatic force.

$W=\int Fdr\\\Rightarrow W = \int \dfrac{kep}{r^2}dr\\\Rightarrow W = kep\int \dfrac{1}{r^2}dr\\\Rightarrow W = kep\left | \dfrac{1}{r} \right |_{y}^{x}\\\Rightarrow W = kep\left ( \dfrac{1}{x}-\dfrac{1}{y} \right )\\\Rightarrow W = kep\left ( \dfrac{1}{x}-\dfrac{1}{\infty} \right )\\\Rightarrow W =\dfrac{kep}{x}$

Using the principle of the work-energy theorem,

As only the electrostatic force is assumed to act between the two charges, the kinetic energy change of the electron will be equal to the work done by the electrostatic force on the electron due to proton.

$\therefore \Delta K = W\\\Rightarrow \dfrac{1}{2}m(v^2-u^2)= \dfrac{kep}{x}\\\Rightarrow \dfrac{1}{2}m((3u)^2-u^2)= \dfrac{kep}{x}\\\Rightarrow \dfrac{1}{2}m(8u^2)= \dfrac{kep}{x}\\\Rightarrow x= \dfrac{2kep}{8mu^2}\\\Rightarrow x= \dfrac{2\times 9\times 10^9\times 1.6\times10^{-19}\times 1.6\times10^{-19}}{8\times 9.1\times10^{-31}\times (4.60\times 10^5)^2}\\\Rightarrow x=2.99\times 10^{-10}\ m\leq$

Hence, the electron is at a distance of $2.99\times 10^{-10}\ m$ when the electron instantaneously has speed of three times the initial speed.

8 0

4 years ago

AQ5. What is a car’s speed in m/s if it travels: Remember to write the speed number WITH the correct unit.

AVprozaik [17]

Answer:A

Explanation:

7 0

3 years ago

Read 2 more answers

Qual a massa de água a 45 °C que devemos misturar com 200 g de água a 15 °C, para que o sistema entre em equilíbrio térmico a 35

Stells [14]

Responda:

400 g

Explicação:

Dado o seguinte:

Deixe Mass (m1) = m em t1 = 45 ° C

Massa (m2) = 200g em t2 = 15 ° C

Equilíbrio térmico (T) = 35 ° C

Usando a relação:

m1 * C * ΔT = m2 * C * ΔT

Onde m1 e m2 são as massas; C = capacidade de calor específico da água e ΔT é a mudança de temperatura

m1 * ΔT = m2 * ΔT

m * (45 ° C - 35 ° C) = 200 * (35 ° C - 15 ° C)

10 * m = 200 * 20

10 * m = 4000

m = 4000/10

m = 400g

5 0

3 years ago

1. Your friend is bragging about his motorcycle. He claims that it can go from a stopped position to 50 miles per hour in three

german

He is describing the motorcycle's acceleration.

7 0

3 years ago

What expression gives the amount of light energy (in J per photon) that is converted to other forms between the fluorescence exc

erastovalidia [21]

Answer:

E = hf or $E=\dfrac{hc}{\lambda}$

Explanation:

The expression that gives the amount of light energy that is converted to other forms between the fluorescence excitation and emission events is given by :

E = hf

f is the frequency

$E=\dfrac{hc}{\lambda}$

c is the speed of light

$\lambda$ is the wavelength

Hence, this is the required solution.

8 0

3 years ago