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3 years ago

A 2.5g copper penny is given a charge of -4.0*10^-9c. how mny excess electrons are on the penny?

Physics

1 answer:

Lyrx [107]3 years ago

7 0

Answer : The excess of electrons on the penny are, $2.5\times 10^{10}$ electrons

Solution : Given,

Total charge = $-4.0\times 10^{-9}C$

Charge on electron = $-1.6\times 10^{-19}C$

Formula used :

$\text{Excess of electrons}=\frac{\text{Total charge}}{\text{Charge of electron}}$

Now put all the given values in this formula, we get the excess of electrons present on the penny.

$\text{Excess of electrons}=\frac{\text{Total charge}}{\text{Charge of electron}}=\frac{-4.0\times 10^{-9}C}{-1.6\times 10^{-19}C/e^-}=2.5\times 10^{10}e^-$

Therefore, the excess of electrons on the penny are, $2.5\times 10^{10}$ electrons

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2. A Formula One race car speeds up from rest to 27.8 m/s in a distance of 25 meters.

Nadya [2.5K]

Answer:

Correct answer: a = 15.46 m/s²

Explanation:

The formula for accelerated movement with the given data is:

V² - V₀² = 2 · a · d where the initial velocity V₀ and the final V

Since the initial velocity V₀ is zero, the formula is:

V² = 2 · a · d => a = V² / (2 · d) = 27.8² / (2 · 25) = 772.84 / 50 = 15.46 m/s²

a = 15.46 m/s²

God is with you!!!

4 0

3 years ago

How many kilohertz are<br> 750 megahertz?

e-lub [12.9K]

Answer:

750,000

Explanation:

I just looked it up on Google lol. You apparently multiple by 1000

Hope this helps :p

7 0

3 years ago

Read 2 more answers

A heavy flywheel is accelerated (rotationally) by a motor that provides constant torque and therefore a constant angular acceler

ki77a [65]

Answer:

a) $t_1=\frac{w_1-w_o}{\alpha}=\frac{w_1}{\alpha}sec$

b) $\theta_1=\frac{w_1^2}{2\alpha}rad$

c) $t_2=\frac{\alpha t_1}{5\alpha}=\frac{t_1}{5}sec$

Explanation:

1) Basic concepts

Angular displacement is defined as the angle changed by an object. The units are rad/s.

Angular velocity is defined as the rate of change of angular displacement respect to the change of time, given by this formula:

$w=\frac{\Delat \theta}{\Delta t}$

Angular acceleration is the rate of change of the angular velocity respect to the time

$\alpha=\frac{dw}{dt}$

2) Part a

We can define some notation

$w_o=0\frac{rad}{s}$ ,represent the initial angular velocity of the wheel

$w_1=?\frac{rad}{s}$ , represent the final angular velocity of the wheel

$\alpha$ , represent the angular acceleration of the flywheel

$t_1$ time taken in order to reach the final angular velocity

So we can apply this formula from kinematics:

$w_1=w_o +\alpha t_1$

And solving for t1 we got:

$t_1=\frac{w_1-w_o}{\alpha}=\frac{w_1}{\alpha}sec$

3) Part b

We can use other formula from kinematics in order to find the angular displacement, on this case the following:

$\Delta \theta=wt+\frac{1}{2}\alpha t^2$

Replacing the values for our case we got:

$\Delta \theta=w_o t+\frac{1}{2}\alpha t_1^2$

And we can replace $t_1$ from the result for part a, like this:

$\theta_1-\theta_o=w_o t+\frac{1}{2}\alpha (\frac{w_1}{\alpha})^2$

Since $\theta_o=0$ and $w_o=0$ then we have:

$\theta_1=\frac{1}{2}\alpha \frac{w_1^2}{\alpha^2}$

And simplifying:

$\theta_1=\frac{w_1^2}{2\alpha}rad$

4) Part c

For this case we can assume that the angular acceleration in order to stop applied on the wheel is $\alpha_1 =-5\alpha \frac{rad}{s}$

We have an initial angular velocity $w_1$ , and since at the end stops we have that $w_2 =0$

Assuming that $t_2$ represent the time in order to stop the wheel, we cna use the following formula

$w_2 =w_1 +\alpha_1 t_2$

Since $w_2=0$ if we solve for $t_2$ we got

$t_2=\frac{0-w_1}{\alpha_1}=\frac{-w_1}{-5\alpha}$

And from part a) we can see that $w_1=\alpha t_1$ , and replacing into the last equation we got:

$t_2=\frac{\alpha t_1}{5\alpha}=\frac{t_1}{5}sec$

5 0

3 years ago

Q5: An ice skater moving at 12 m/s coasts

ExtremeBDS [4]

u = 0.077

Explanation:

Work done by friction is

Wf = ∆KE + ∆PE

-umgx = ∆KE,. ∆PE =0 (level ice surface)

-umgx = KEf - KEi = -(1/2)mv^2

Solving for u,

u = v^2/2gx

= (12 m/s)^2/2(9.8 m/s^2)(95 m)

= 0.077

8 0

3 years ago

Joan needs to eliminate some employees for a short while. She and her managers identify those employees who are not meeting perf

tigry1 [53]

Answer: layoff

Explanation:

From the information in the question, we can see that Jane is trying to reduce the size of the workforce here through layoff.

Since Joan explains that the termination is temporary, then it's a layoff. If it were to be firing, the termination won't be temporary but permanent as they can't be recalled by the company. But since the employees are discharged temporarily, it's a layoff.

4 0

3 years ago