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vodka [1.7K]
2 years ago
9

Negative charges repel positive charges. a. true or b. false

Physics
1 answer:
arlik [135]2 years ago
6 0
False they attract.. Remember opposites attract!
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If vector A =i+2j-k and vec A cross vec B =3i-j+5k. find vec B​​​
postnew [5]

Let <em>B</em> = <em>a</em> <em>i</em> + <em>b</em> <em>j</em> + <em>c</em> <em>k</em>. Then the cross product of <em>A</em> = <em>i</em> + 2<em>j</em> - <em>k</em> with <em>B</em> is

<em>A</em> × <em>B</em> = ( <em>i</em> + 2<em>j</em> - <em>k </em>) × ( <em>a</em> <em>i</em> + <em>b</em> <em>j</em> + <em>c</em> <em>k</em> )

<em>A</em> × <em>B</em>  = <em>a</em> ( <em>i</em> × <em>i</em> ) + 2<em>a</em> ( <em>j</em> × <em>i</em> ) - <em>a</em> ( <em>k</em> × <em>i </em>)

… … … + <em>b</em> ( <em>i</em> × <em>j</em> ) + 2<em>b</em> ( <em>j </em>× <em>j</em> ) - <em>b</em> ( <em>k</em> × <em>j</em> )

… … … + <em>c</em> ( <em>i</em> × <em>k</em> ) + 2<em>c</em> ( <em>j</em> × <em>k</em> ) - <em>c</em> ( <em>k</em> × <em>k</em> )

<em>A</em> × <em>B</em> = 0 - 2<em>a</em> <em>k </em>- <em>a</em> <em>j</em>

… … … + <em>b</em> <em>k</em> + 0 + <em>b</em> <em>i</em>

… … … - <em>c</em> <em>j</em> + 2<em>c</em> <em>i</em> - 0

<em>A</em> × <em>B</em> = (<em>b</em> + 2<em>c</em>) <em>i</em> + (-<em>a</em> - <em>c</em>) <em>j</em> + (<em>b</em> - 2<em>a</em>) <em>k</em>

So we have

3 <em>i</em> - <em>j</em> + 5 <em>k </em>= (<em>b</em> + 2<em>c</em>) <em>i</em> + (<em>c</em> - <em>a</em>) <em>j</em> + (<em>b</em> - 2<em>a</em>) <em>k</em>

which gives us the system of equations,

{ <em>b</em> + 2<em>c</em> = 3

{ -<em>a</em> - <em>c</em> = -1

{ -2<em>a</em> + <em>b</em> = 5

Solve for <em>a</em>, <em>b</em>, and <em>c</em>.

• Eliminate <em>c</em> from the first two equations:

(<em>b</em> + 2<em>c</em>) + 2 (-<em>a</em> - <em>c</em>) = 3 + 2 (-1)

-2<em>a</em> + <em>b</em> = 1

But -2<em>a</em> + <em>b</em> = 5, and 5 ≠ 1, so there is no such vector <em>B</em> that satisfies the cross product!

8 0
2 years ago
What is the speed of a wave that has a frequency of 45 Hz and a wavelength of 0.1 meters?
Yuri [45]
<span>λν=c
(wavelength x frequency = speed)

speed = 45 x 0.1
= 4.5 m/s</span>
6 0
3 years ago
Read 2 more answers
Therese plays lacrosse, but she has injured her ankle and has to take a few weeks off. She is finding that she has a lot of trou
vivado [14]

Answer: No endorphins

Explanation: cuz' she injured her ankle

6 0
3 years ago
Calculate the work efecttuated, when the force is 300 N, and the distance is 300 meters.
Alexxx [7]

Hello!

Use the formula:

W = Fd

Replacing:

W = 300 N * 300 m

Resolving:

W = 90000 J

The work is <u>90000 Joules.</u>

8 0
3 years ago
Read 2 more answers
A wave is travelling at 3000 m/s has a wavelength of 1 m.
Levart [38]

Answer:

a] 3000hz

b]3.33 × 10⁻⁴

ci]300

ii] 3000

iii]60,000

Explanation:

3 0
3 years ago
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