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3 years ago

Which of the following electromagnetic waves is not used for communication?

1 answer:

8 0

Microwaves and radio waves are employed in radio and satellite communications while infrared waves are used in remote controls and infrared features of new phones and other electrons. However, gamma rays have far too much energy and cause damage to the body. They are not used in communication.
The answer is A.

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Which of the following results when a crest and trough meet?

kifflom [539]

D. Destructive interference. An easy way to think about it is the waves are opposite each other, so they essentially cancel each other out, or make an effort to.

6 0

3 years ago

5. Calculate the final speed of a 110-kg rugby player who is initially running at 8.00 m/s but collides head-on with a padded go

bulgar [2K]

Answer:

0.8 m/s

Explanation:

From Newton's third law of motion,

Impulse on a body = Change in momentum of the body

Ft = m(v-u) ......................... Equation 1

Where F = force on the body , t = time, m = mass of the body, v = final velocity, u = initial velocity,

Note: Taking the direction of the initial velocity as negative,

Given: F = 1.76×10⁴ N, t = 5.5×10⁻² s, m = 110 kg, u = -8.0 m/s

Substitute into equation 1

1.76×10⁴ ( 5.5×10⁻²) = 110[v-(-8.0)]

968 = 110v+880

110v = 968-880

110v = 88

v = 88/110

V = 0.8 m/s

Hence the final velocity = 0.8 m/s

4 0

4 years ago

3. Apple juice is an example of a(n) ________. (SC.8.P.8.9)

trapecia [35]

Answer:

The answer is definitely Water

8 0

3 years ago

A decorative plastic film on a copper sphere of 10 mm diameter in an oven at 750C. Upon removal from the oven, the sphere is sub

AlladinOne [14]

Answer:

3.26 secs

Explanation:

Diameter of sphere ( D )= 10 mm

T1 = 75°C

P = 1 atm

T∞ = 23°C

T2 = 35°c

Velocity = 10 m/s

<u>Determine how long it will take to cool the sphere to 35°C</u>

<em>Using the properties of copper and air given in the question</em>

Nu = 2 + (Re)^0.8 (Pr)^0.33

hd / k = 2 + ( vd/v )^0.8 (Pr)^0.33

∴ h ≈ 2594.7 W/m^2k

Given that :

(T2 - T∞) / ( T1 - T∞ ) = exp [ ( -hA / pv CP ) t ]

( 35 - 23 ) / ( 75 - 23 ) = exp [ - 2594.7 * 6 * t / 8933 * 387 * 10 * 10^-3 ]

= ln ( 12/52 ) = -1.466337069 = - 0.45032919 * t

∴ t ≈ 3.26 secs ( -1.466337069 / -0.45032919 )

6 0

3 years ago

frictional force acting on a 0.5 kg object and a floor is 3 N. What is the coefficient of friction between the object and the fl

ikadub [295]

Answer:

μ = 0.6

Explanation:

F = μN

N = mg

F = μmg

3 N = μ*0.5 kg * 9.8 m/s²

μ = 3/(0.5*9.8) = 0.6

7 0

3 years ago